Dissertations / Theses: 'Herbivorie'

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Amasifuen, Guerra Carlos Alberto. "Étude écologique et biochimique de Himatanthus tarapotensis (Apocynaceae) : patrons de production et rôle dans l’interaction plante – insecte de la pluméricine, en milieu naturel amazonien." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT111/document.

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Himatanthus tarapotensis (Apocynaceae) connu au Pérou comme "bellaco caspi", est un arbre répandu dans plusieurs types d’habitat de l’Amazonie péruvienne où il est très utilisé en médicine traditionnelle pour le traitement de certaines maladies. Les propriétés médicinales des espèces de Himatanthus sont liées notamment à la présence du terpène bioactif pluméricine. Le potentiel pharmacologique de la pluméricine et le succès reproductif de H. tarapotensis ont mené à la réalisation de cette étude afin d’explorer les patrons de production de ce composé le long des variations des gradients environnementaux déterminés par les différents types d’habitat où la plante pousse naturellement. Cependant, il existe une confusion autour de la délimitation des espèces du genre Himatanthus qui pousseraient au Pérou et les noms scientifiques qui doivent être utilisés. En conséquent une partie de cette étude a consisté en l’évaluation taxonomique du genre Himatanthus. Dans la première partie de la thèse est présentée une révision synoptique des espèces de Himatanthus de l'Amazonie péruvienne, avec la finalité d'introduire une stabilité taxonomique de ces espèces au Pérou. Trois espèces de Himatanthus se trouvent au Pérou : H. tarapotensis, H. phagedaenicus et H. revolutus, distinguées entre eux notamment par des traits reproductifs. Dans la seconde partie, les feuilles d’individus juvéniles de H. tarapotensis qui se développent sur deux types d’habitat ont été prélevées pour évaluer la production de pluméricine en fonction des facteurs environnementaux : type de sol, période de précipitations, et pression des insectes en tenant compte de la croissance de la plante. La production de pluméricine chez H. tarapotensis ne montre pas différences significatives en fonction des types de sol. Mais, il a été observé une variation temporelle de la concentration du composé corrélée positivement avec la pression des insectes, notamment avec la larve herbivore Isognathus leachii (Lepidoptera : Sphingidae) et négativement avec la croissance. En même temps, ces deux facteurs ont été corrélés avec la précipitation, ce qui suggère que l’intensité de pluie influencerait la production de pluméricine de manière indirecte. Le composé bioactif pluméricine pourrait avoir un patron de production déterminé par son rôle médiateur des interactions de H. tarapotensis avec son environnement
Himatanthus tarapotensis (Apocynaceae) known in Peru as "bellaco caspi", is a common tree from several habitats in the Peruvian Amazon, where is widely used in traditional medicine for the treatment of various diseases. Medicinal properties from species of Himatanthus have been mainly related to the presence of a bioactive terpene plumericin. The pharmacological potential of plumericin and reproductive success of H. tarapotensis gave rise to the present study to explore the production patterns of this compound in function of environmental gradients determined by the different habitat types where this species grows in nature. However, the delimitation of Himatanthus species has long been problematic, and much confusion remains as to which names should be used and which species delimitations should be adopted. Consequently, a part of this study was dedicated to a taxonomic revision of Himatanthus species occurring in Peru. Therefore, in chapter 1 is presented a synoptic revision of Himatanthus species from the Peruvian Amazon, with the aim of introducing taxonomic stability of those species in Peru. Three species of Himatanthus are present in Peru: H. tarapotensis, H. phagedaenicus and H. revolutus, distinguished among themselves mainly by reproductive traits. In chapter 2, leaves collected from juvenile individuals of H. tarapotensis growing on two Amazonian habitats were used to evaluate the plumericin production in relation to environmental factors: soil type, period of precipitation, and insects pressure, keeping in mind their relation with the growth patterns of the plant. Plumericin production in H. tarapotensis was not affected by differences in soil types. However, it was observed a temporal variation in the concentration of this compound correlated positively to the insects pressure, mainly with the herbivorous larva of Isognathus leachii (Lepidoptera: Sphingidae) and negatively to the growth pattern of the plant. These two factors were correlated to the rainfall, thus suggesting that precipitation would be affecting indirectly on plumericin production. The bioactive compound plumericin would have a production pattern determined by its mediator role in interactions phenomena of H. tarapotensis and its environment

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Brugneaux, Sophie. "Régulation des communautés algales par les macro-herbivores dans les communautés récifales des Antilles françaises : (Guadeloupe, Martinique, Saint-Barthélémy)." Thesis, Antilles-Guyane, 2012. http://www.theses.fr/2012AGUY0522/document.

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Une étude des facteurs influençant la composition et la répartition spatiale des abondances algales dans les communautés récifales des Antilles françaises et plus spécifiquement de Guadeloupe a été réalisée. Le rôle joué par les oursins diadème est plus particulièrement étudié. Les principaux compartiments des communautés récifales et les facteurs d'influence susceptibles de jouer un rôle dans la régulation du compartiment algal ont été dimensionnés sur 22 stations des Antilles françaises. Pour cela plusieurs indicateurs ont été testés. Après une description de chaque compartiment biotique (algues, herbivores, prédateurs), une recherche des facteurs influençant les caractéristiques du compartiment algal a été menée à trois échelles spatiales, à l'aide d'analyses statistiques non paramétriques, notamment des analyses canoniques des redondances et des correspondances. Puis, une recherche des facteurs influençant la répartition des oursins diadème a été également menée. Si les deux guildes d'herbivores étudiées (poissons et oursins diadème) ont un impact significatif sur l'abondance de gazon algal, seuls les poissons herbivores ont la capacité d'exercer cette influence à l'échelle des récifs de Guadeloupe et cette influence ne s'étend pas aux autres catégories algales. Notamment les phéophycées. A l'échelle de l'ensemble des îles étudiées, les analyses effectuées n'ont pas permis de mettre en évidence l'influence des herbivores sur la régulation des abondances algales. Les oursins diadèmes sont en faible densité dans les iles antillaises étudiées. Plusieurs facteurs susceptibles de participer à leur répartition en taille et en abondance sont identifiés
A study of factors influencing the composition and spatial distribution of algal abundance in the French Caribbean reef communities and more specifically in Guadeloupe was conducted. The role of diadema sea urchins was particularly studied. For that, 22 stations in the French Antilles were selected and several indicators tested. After a description of each biotic compartment (algae, herbivore, predators), a search for factors influencing the characteristics of the algal compartment was conducted at three spatial scale, using non-parametric statistical analyses, including canonical correspondence analyses (cca) and redundancy analyses (rda). Then a search for the factors influencing the distribution of diadema sea urchins was also conducted. If the two guilds of herbivores (diadema sea urchin and fish) have a significant impact on the abundance of algal turf, only herbivorous fish was found to have an influence in the reefs of Guadeloupe and that influence was not observed on other algal groups, including phaeophyceae. At the scale of all the islands, the analyses did not enable to show the influence of herbivores in the regulation of algal abundance. The density of sea urchins was found to be low in the studied sites. Several factors likely to influence their distribution in size and their abundance were identified

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Ye, Lambiénou. "Stratégies des Graminées pour le recyclage des nutriments et herbivorie." Paris 6, 2013. http://www.theses.fr/2013PA066324.

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L’objectif de cette thèse portant sur une savane arbustive sèche du Burkina Faso est de déterminer, par un échantillonnage de terrain et une mise en exclos, les effets des Graminées en interaction avec le bétail sur le recyclage des nutriments. J’ai décrit une zone aux sols peu profonds, dominée par les Graminées annuelles et plus fréquentée par le bétail et une zone aux sols profonds, dominée par les Graminées pérennes et peu fréquentée par le bétail. Les Graminées pérennes A. Ascinodis et A. Gayanus sont susceptibles de mieux contrôler le recyclage de l’azote par rapport aux Graminées annuelles A. Pseudapricus et L. Togoensis. Les pérennes produisent une biomasse racinaire plus élevées que les annuelles. L’activité biologique du sol est plus importante sous les deux Graminées pérennes que sous les deux annuelles. Avec des teneurs en ammonium plus élevées et des valeurs de N15 du sol plus faibles sous les pérennes, ces espèces de Graminées paraissent inhiber la nitrification. Cependant A. Ascinodis mais pas A. Gayanus augmente la teneur du sol en carbone organique. Enfin, à court terme (effet des exclos), le pâturage n’a pas un effet significatif sur les teneurs en carbone et azote total et en phosphore assimilable. Le pâturage diminue la respiration basale du sol mais pas la biomasse microbienne. Le pâturage favorise les graminées annuelles par rapport aux pérennes et diminue la richesse spécifique herbacée. L’ensemble de la thèse confirme que les graminées annuelles sont une marque de dégradation des pâturages et de perte de fertilité et suggère que ce lien est dû à la meilleur capacité de contrôle du recyclage des nutriments minéraux par les pérennes
The objective of this thesis is to determine the impacts of grasses, in interaction with grazing by cattle, on nutrient cycling. This is achieved through field sampling and exclosures in a dry savanna of Burkina Faso. I have described a zone of shallow soils dominated by annual grasses and highly frequented by cattle and a zone with deeper soils dominated by perennial grasses and less frequented by cattle. The perennial grasses, A. Ascinodis and A. Gayanus, likely better control nutrient cycling than the annual grasses, A. Pseudapricus and L. Togoensis. Perennials have a higher root biomass than annuals. Soil biological activity is higher in the soil of perennials than in the soil of annuals. Ammonium availability is higher and soil N15 is smaller under perennials, which suggests that perennials but not annuals are able to inhibit nitrification. However, A. Ascinodis but not A. Gayanus increases soil concentration in organic carbon. On the short term, cattle impact neither soil total C and N, nor the available P. Cattle also decrease soil basal respiration but do not affect microbial biomass. Cattle favor the abundance of annuals relatively to the abundance of perennials and decrease the richness in herbaceous species. Overall, my thesis confirms that annuals are a mark of pasture degradation and decrease in fertility. My results suggest that this is due to the capacity of perennials to better control nutrient cycling and decrease nutrient losses

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Bernard, Marianne. "Changements climatiques et herbivorie : influence sur la régénération et le potentiel d'avenir des forêts mélangées." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG052/document.

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L’inquiétude au sujet du devenir des forêts tempérées de moyenne montagne va croissant, du fait du changement climatique d’une part, et des difficultés de régénération liées à la pression exercée par les grands ongulés d’autre part. Les populations d’ongulés herbivores connaissent en effet une forte augmentation depuis le milieu du XXème siècle dans l’hémisphère Nord ; et leur abroutissement sélectif, dû à leurs préférences alimentaires, exerce une forte pression sur la régénération, dont l’intensité sur les essences varie selon leur appétence. La réponse de la régénération au changement climatique en termes de survie et de croissance demeure méconnue, mais de premiers résultats suggèrent qu’elle pourrait être encore plus affectée que les arbres adultes, et de manière différentielle également du fait des diverses autécologies des essences. Dans ce contexte de changements globaux, le recours aux forêts mélangées est envisagé comme une option valable de minimisation des risques. Comment caractériser la réponse de la régénération à ces deux pressions de sélection, et quel pourrait être l’avenir d’un peuplement mélangé dans ce contexte ? Notre étude se focalise sur les effets de l’abroutissement par les grands ongulés et du changement climatique sur la régénération du sapin, du hêtre et de l’épicéa en mélange. Nous utilisons pour cela diverses approches. Nous montrons que la germination et l’installation de semis de hêtres n’est pas affectée par l’éclairement au sol plus faible en situation de mélange. Nous mettons en évidence une quasi-inversion d’essences entre sapin et épicéa au niveau de la strate de régénération, bénéficiant à l’épicéa, lorsqu’ils sont soumis à une forte pression d’abroutissement. A l’échelle des traits foliaires, nous trouvons des réponses différentes entre les trois essences aux pressions du climat et de l’abroutissement, le sapin étant le seul à exprimer une réponse claire à l’abroutissement (tissus plus résistants, augmentation du rapport C/N foliaire). Nos résultats démontrent également une diminution de l’abroutissement avec l’augmentation de la température hivernale et un effet plus important de l’abroutissement que de la température printanière sur la croissance des semis de sapin, hêtre, érable. Enfin, via une approche de modélisation, nous avons simulé la dynamique d’un peuplement mélangé de sapin, hêtre et épicéa sur une durée de 100 ans, et montré une modification des seuils de tolérance à la sécheresse par l’abroutissement, et vaildé la possible disparition du sapin dans des scénarios comprenant abroutissement et changement climatique. Ces travaux soulignent l’influence des grands ongulés en interaction avec les conditions climatiques sur la dynamique de la régénération forestière, et l’importance de prendre cette pression en compte dans les protocoles de recherche destinés à étudier l’évolution de la régénération en contexte climatique changeant
There is growing concern about the future of temperate mountainous forests, because of climate change and of the difficulties in regenerating forests caused by large ungulates pressure. Herbivore ungulate populations have strongly increased since the middle of the XXth century in the northern hemisphere. By their selective browsing due to their dietary preferences, they exert a strong pressure on regeneration, which intensity on each tree species varies with their palatability. The response of regeneration to climate change in terms of growth and survival is still poorly known, but some results suggest it could be affected differentially given the different autecologies of the species. In such a global changes context, mixed forests are considered a valuable option of adaptation. How would the regeneration phase respond to those two pressures, and what could be the future of a mixed stand in such a context? This study focuses on the effects of browsing by large ungulates and climate change on mixed silver fir, Norway spruce and beech stand regeneration. We show that the lower amount of light reaching the ground in mixed stands does not affect beech regeneration germinating. We demonstrate a quasi-substitution of silver fir by Norway spruce saplings when submitted to high browsing pressure. At the finer scale of foliar traits, we find different responses among the three species to varying climate and browsing pressure, silver fir being the only species expressing an answer to browsing (increase in shoot mechanical resistance and in foliar C:N). Our results also demonstrate a decrease in browsing with increasing winter temperature, and a stronger effect of browsing than of spring temperature on saplings growth for silver fir, beech and sycamore maple. Finally, our simulations of the dynamics of a mixed silver fir-Norway spruce-beech stand suggest a shift in tolerance to drought thresholds due to browsing, and confirm the possible eradication of silver fir in scenarios combining browsing and climate change. This work highlights the influence of large ungulates interacting with climate conditions on forest regeneration dynamics, and the importance to consider this pressure in research protocols aiming at studying the behaviour of regeneration in changing climate contexts

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Scheidel, Ulrich. "Die Bedeutung der Herbivorie für die Verbreitung montaner Compositen im Harz : mit 26 Tab. im Text /." Berlin ; Stuttgart : Cramer in der Gebr.-Borntraeger-Verl.-Buchh, 2001. http://www.gbv.de/dms/bs/toc/334938163.pdf.

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Barrere, Julien. "Interactions entre chêne et cervidés durant le processus de renouvellement - cas des peuplements forestiers tempérés de plaine (Quercus robur et Q. petraea)." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0285.

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Les cervidés ont vu leur abondance et leur distribution spatiale augmenter fortement depuis les dernières décennies, en France, et plus généralement à l’échelle de l’hémisphère Nord. Si ces espèces jouent un rôle clé dans le fonctionnement des écosystèmes forestiers, le niveau actuel des populations compromet le processus de régénération forestière de certaines essences cruciales pour la filière sylvicole telles que les chênes sessile et pédonculé (Quercus robur et Q. petraea). L’objectif de cette thèse est de quantifier et décrire les mécanismes sous-jacent de la contrainte exercée par les cervidés sur la régénération et d’identifier dans quelle mesure certaines opérations sylvicoles (coupe, dégagement et pose d’enclos) influencent cette contrainte. L’analyses de la composition de panses de cerf et de chevreuil sur le site de La Petite Pierre (Vosges) a permis de montrer que les glands de chêne représentaient une ressource significative dans le régime alimentaire de ces deux espèces, mais que leur consommation de gland saturait les années de forte fructification. Par des approches expérimentales, nous avons mis en évidence que l’abroutissement de la pousse apicale réduisait toujours la croissance en hauteur des semis que ce soit en condition de terrain, ou en pépinière, et que ce phénomène s’expliquait par une faible plasticité d’allocation des ressources pour compenser la perte de tissu. L’analyse d’un résultats d’un réseau d’enclos-exclos répartis sur plusieurs sites en France et en Suède a permis de montrer que la coupe d’arbre adulte pour augmenter l’ouverture de la canopée accentuait l’effet négatif des cervidés sur la croissance et la survie de jeunes semis de chêne, via une plus forte fréquentation des cervidés dans les patches de régénération ouverts. Enfin, suite à l’implémentant du processus d’herbivorie dans un modèle de dynamique forestière (bibliothèque Régénération de CAPSIS), j’ai effectué des simulations suggérant que sous une forte pression d’herbivorie, des opérations de dégagement moins fréquentes et maintenant des espèces accompagnatrices appétentes comme le charme permettrait de réduire l’influence négative des cervidés sur la croissance du chêne. En conclusion, les résultats de cette thèse étayent l’hypothèse que les cervidés représentent une contrainte significative pour le processus de régénération du chêne, mais suggère qu’une gestion de la végétation de sous-bois adaptée permettrait de réduire cette contrainte et de se rapprocher d’un équilibre plus durable entre faune sauvage et activités sylvicoles
The abundance and spatial distribution of cervids have drastically increased in France, and more generally in the Northern hemisphere over the last decades. These species play a crucial part in the functioning of forest ecosystems, but the current level of their populations compromises the process of forest regeneration for many tree species of crucial importance such as pedunculate and sessile oak (Quercus robur et Q. petraea). The objectives of this thesis are to quantify and unravel the mechanisms underlying the constraint exerted by cervids on oak regeneration through the consumption of acorns, of oak saplings and of admixed understory species, and (ii) to identify how specific forest management operations (i.e. fencing, felling, and clearing) can limit or enhance this constraint. The analysis of a long-term dataset of red and roe deer rumen content sampled in the study site of La Petite Pierre (Northeastern France) showed that acorns represented a significant resource in the diet of these two species, but that their acorn consumption saturated years of high fructification. Using experimental approaches, we showed that simulated deer browsing on the apical shoot systematically reduced oak sapling height growth both in situ and ex situ, and this was explained by a relatively poor plasticity in resource allocation following browsing to compensate for the loss of tissues. The analysis of a network of fenced-unfenced plots located in several sites in France and in Sweden showed that felling to increase canopy openness enhanced the negative effect of cervids on oak sapling growth and survival through a higher frequentation of cervids under open canopies. Lastly, after implementing the process of herbivory in a forest dynamic model (i.e. Regeneration library of CAPSIS modelling tool), I conducted simulations that suggested that under a high browsing pressure, less frequent clearing operations maintaining highly palatable sapling species such as hornbeam could reduce the negative influence of cervids on oak regeneration. To conclude, this thesis results confirm that cervids exert a significant constraint on the process of oak regeneration, but also suggest that adapted management of the understory vegetation could reduce this constraint and contribute to restore a balance between wildlife and silvicultural activities

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Schaal, Gauthier. "Structure et fonctionnement des réseaux trophiques associés aux écosystèmes littoraux rocheux en situation écologiques contrastées : approches isotopiques et biochimiques combinées." Paris 6, 2009. http://hal.upmc.fr/tel-01110855.

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L’objectif de ce travail est de caractériser la structure et le fonctionnement des réseaux trophiques associés aux écosystèmes de la frange infralittorale rocheuse en Bretagne, à canopée de Laminaria digitata ou fortement affectés par l’activité humaine. Contrairement aux études précédentes, le réseau trophique n’apparaît simplifié ni fonctionnellement ni structurellement en milieu anthropisé, probablement en lien avec la complexité topographique de l’habitat, permettant la coexistence de plusieurs voies de transfert trophique menant à des prédateurs exploitant des niches trophiques variées. Les résultats mettent en évidence pour les trois sites étudiés que le réseau trophique se base sur une large diversité de sources et, en particulier, que L. Digitata ne représente pas une source de nourriture majoritaire à l’état frais pour la majorité des consommateurs. L’utilisation de cette algue par les différents groupes trophiques semble toutefois varier en fonction des conditions locales, à l’état fraîche comme sous forme détritique. Enfin, nos résultats montrent un lien entre la microstructure spatiale de l’habitat rocheux et une variabilité de certaines voies de transfert trophiques à très fine échelle. L’ensemble de ces résultats suggère que les écosystèmes rocheux de la frange infralittorale sont caractérisés par une forte diversité fonctionnelle qui contribue au maintien d’une importante biodiversité dans ces milieux

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Gayet, Guillaume. "Colonisation d'un écosystème d'eau douce hétérogène, par un oiseau d'eau herbivore : le cygne tuberculé (Cygnus olor) dans les étangs piscicoles de Dombes." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20119.

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Dans certains cas, la colonisation des zones humides par les espèces animales et végétales peut être une menace majeure pour la biodiversité. Il est donc primordial de mieux connaître l'écologie des espèces colonisatrices pour définir leurs relations avec le reste de l'écosystème. Nous avons étudié les conséquences de la colonisation relativement récente des étangs piscicoles français par le cygne tuberculé (Cygnus olor). Nous nous sommes intéressés à l'expression de cette colonisation dans l'espace par l'étude des processus de sélection de l'habitat. Nos résultats montrent que dans un paysage d'étangs, la répartition des cygnes tuberculés dépend à la fois de la configuration spatiale des étangs (aire isolement), des ressources disponibles et du statut de reproduction des cygnes tuberculés. Nous avons ensuite étudié les interactions entre le cygne tuberculé et les communautés animales et végétales des étangs. Sur les sites de cantonnement des couples, nous n'avons pas montré d'effet de la présence des cygnes tuberculés sur l'abondance des oiseaux d'eau, et aucune forme d'exclusion spatiale à l'échelle de l'étang. En revanche, les cygnes tuberculés peuvent générer une déplétion significative des herbiers de macrophytes aquatiques, suggérant des effets en cascade sur les autres communautés des étangs piscicoles. Comme toute perturbation générée par une espèce colonisatrice, celle associée à l'arrivée des cygnes doit néanmoins être replacée dans le contexte plus large des régimes de perturbations à l'oeuvre sur l'écosystème, ce qui importe particulièrement dans le cas d'écosystèmes aussi dépendants de l'activité humaine que les étangs piscicoles
In some cases, wetland colonization by animals and plants may be a major threat to biodiversity. It is therefore crucial to better understand the ecology of colonizing species to assess their relationships with the other elements of ecosystems. We studied the consequences of the relatively recent colonization of French fishponds by mute swan (Cygnus olor). We especially considered how such colonization now translates into space, through the analysis of habitat selection processes. Our results show that swan distribution within a fishpond landscape depends on fishpond spatial configuration (area isolation), available resources as well as mute swan breeding status. We then analysed the relationships between mute swan and fishpond animal and plant communities. Where swan pair settle, we do not demonstrate any effect of swan presence on the abundance of other waterbirds, nor any spatial exclusion within fishponds. Conversely, mute swans can signif icantly deplete aquatic macrophyte beds, suggesting cascade effects on other fishpond communities are possible. Like any perturbation caused by a colonizing species, that associated with swan arrival however has to be considered in the broader context of perturbation regimes onto the ecosystem. This is especially crucial in ecosystems like fishponds, that are so much dependent upon human activity

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Elger, Arnaud. "Herbivorie et stratégies adaptatives des végétaux : étude expérimentale de la palatabilité des macrophytes aquatiques des zones humides fluviales." Lyon 1, 2002. http://www.theses.fr/2002LYO10144.

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La relation entre la palatabilité des macrophytes aquatiques et leur distribution sur les gradients de stress nutritionnel et de perturbation par les crues a été étudiée dans les zones humides du Rhône et de l'Ain (France). La végétation aquatique de 33 anciens chenaux fluviaux a été échantillonnée, et le taux de consommation du Gastéropode Lymnaea stagnalis (L. ) a été mesuré en laboratoire sur les 41 espèces de macrophytes les plus fréquentes. Parallèlement, les niveaux de perturbation et de stress ont été évalués dans chaque chenal. Le taux de consommation de L. Stagnalis varie fortement selon les espèces de macrophytes, et peut donc être utilisé comme un indice de palatabilité. Une corrélation positive a été mise en évidence entre la palatabilité des macrophytes et le niveau de perturbation de leur habitat. La palatabilité des macrophytes n'est pas directement influencée par le niveau de stress de leur habitat, mais dépend de l'interaction entre ce paramètre et le niveau de perturbation, la relation positive entre la palatabilité des macrophytes et le niveau de perturbation s'estompant à mesure que le niveau de stress diminiue. Des expériences complémentaires, notamment sur des espèces invasives appartenant au genre Elodea, ont permis d'attribuer ces différences de palatabilité à des patrons divergents d'allocation des ressources entre les processus de défense et de croissance du végétal. Le processus de défense serait favorisé lorsque l'environnement est stable et la pression de broutage élevée, alors que le processus de croissance serait favorisé en milieu perturbé, permettant à la plante d'accomplir son cycle de développement entre deux perturbations. Cette tendance est exacerbée en milieu stressant, mais tend à disparaître lorsque la disponibilité des ressources augmente

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Loranger, Jessy. "Prédiction des dommages foliaires causés par les herbivores invertébrés dans une prairie expérimentale à partir des traits des plantes." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/5758.

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Les herbivores invertébrés sont présents dans presque tous les habitats de la planète et peuvent grandement affecter la performance des plantes en nature. Que ce soit en communautés naturelles ou artificielles, une grande variation des taux d'herbivorie entre différentes espèces de plante [i.e. plantes] peut être observée. Ceci s'explique par le fait que les caractéristiques fonctionnelles des plantes, aussi appelées « traits », affectent les préférences des herbivores. Une espèce de plante, de par ces traits physiologiques, morphologiques ou phénologiques, peut donc décourager et/ou éviter l'herbivorie. La compréhension des relations entre les herbivores invertébrés et les traits des plantes est donc indispensable à la compréhension de l'assemblage des communautés herbivores-plantes. Cependant, les connaissances sur les liens entre les différents traits des plantes et la préférence des herbivores sont diffuses et incomplètes. Ce mémoire vise donc à quantifier et caractériser les effets de plusieurs traits fonctionnels de plantes herbacées sur la quantité de dommage foliaire faite par des herbivores invertébrés et à comparer ces effets entre monocultures et polycultures. Pour ce faire, j'ai participé au projet du Jena Experiment , une prairie expérimentale située en Allemagne visant à étudier la biodiversité. Cette prairie est exposée aux herbivores invertébrés naturels se trouvant sur le site de l'étude. Pour réaliser mon projet, les degrés d'herbivorie causés par les invertébrés ainsi que les valeurs de plusieurs traits fonctionnels des plantes ont été mesurés pour chacune de 51 espèces de plante [i.e. plantes] se trouvant sur le site d'étude. Travaillant d'abord avec des monocultures, sept traits sur 42 mesurés ont été sélectionnés dans une régression multiple en tant que prédicteurs importants de l'herbivorie. Le modèle est robuste et explique 63% de la variation en dommage subi par les espèces à l'étude. Parmi ces sept traits, deux sont physiologiques (concentration de lignine et d' azote dans les feuilles), deux sont morphologiques (architecture des racines et érection de la tige), un est phénologique (durée de vie du feuillage) et deux sont reliés aux herbivores (nombre d'espèces de coléoptère et d'hémiptère pouvant potentiellement prédater les plantes). Dans une seconde étape, à partir de l'herbivorie mesurée en monoculture et des sept traits sélectionnés dans le premier volet, trois modèles ont été développés pour prédire l'herbivorie dans des communautés formant un gradient de biodiversité de une à 60 espèces de plantes. Pour les trois différents modèles, le pouvoir de prédiction était faible; de 6 à 32% de variance en dommage foliaire expliquée. De plus, la déviation entre valeurs observées et valeurs prédites de l'herbivorie augmentait significativement avec l'augmentation du niveau de biodiversité dans les communautés. Les résultats de ce mémoire suggèrent que des patrons complexes de corrélation entre les différents traits des plantes existent et qu'il est donc nécessaire de travailler avec le plus de traits possibles pour identifier ceux qui contrôlent vraiment l'herbivorie. De plus, des interactions entre les différentes espèces de plante [i.e. plantes] d'une communauté semblent affecter de façon importante, directement ou pas, les dommages foliaires infligés par les herbivores invertébrés.Les conclusions de ce mémoire remettent en question l'importance relative des traits agrégés pour prédire des processus écologiques à facteur biotique tel que l'herbivorie et soulignent la complexité des relations entre deux niveaux trophiques.

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Guignabert, Arthur. "Etude des processus de régénération naturelle du pin maritime en contexte de dune forestière gérée : influence de la sylviculture, du climat et des interactions biotiques." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0437/document.

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Les forêts dunaires d’Aquitaine de pin maritime (Pinus pinaster) représentent un intérêt économique et écologique important de par leur rôle multifonctionnel (production de bois,protection contre l’érosion, préservation de la biodiversité, tourisme). La régénération naturelle est pratiquée après coupe rase pour les renouveler. Mais, de nombreux échecs de régénération sont observés depuis 20 ans, entrainant des pertes économiques non négligeables.L’objectif de ce travail a été d’identifier les mécanismes écologiques impliqués dans ces échecs récurrents, afin de proposer des recommandations de gestion pour favoriser le renouvellement de ces pinèdes. Pour cela, nous avons étudié quatre étapes-clés du processus de régénération : dispersion des graines, germination, survie, et croissance. Un réseau de sites d’observation le long du cordon dunaire a été utilisé pour quantifier la régénération, en interactions avec des pratiques sylvicoles (coupe rase vs coupe progressive, semis de graines de pin maritime vs absence de semis). Deux sites semi-expérimentaux ont été installé afin d’étudier en détail certains facteurs explicatifs potentiellement importants dans notre contexte(climat, interactions plante-plante, herbivorie). Nos résultats confirment que la régénération naturelle est un processus complexe, influencé par de nombreux facteurs environnementaux et d’autres liés à la gestion, pouvant être eux mêmes en interaction. La quantité de graines atteignant le sol ne semble pas être limitante. La germination des graines est fortement liée à l’humidité du sol, et est influencée par l’hétérogénéité de la microtopographie. La sécheresse estivale, cause majeure de mortalité des plantules, peut-être modulée par le maintien d’arbres semenciers. Les interactions biotiques directes et indirectes avec la végétation de sous-bois impactent fortement la survie des plantules, mais varient grandement en direction et en intensité selon les saisons et les années.Bien que nos résultats permettent de mieux comprendre les mécanismes impliqués dans le cycle de régénération du pin maritime, il apparaît difficile de mettre en avant un seul facteur expliquant les échecs de régénération sur certains secteurs. Cependant, dans l’ensemble, le maintien d’arbres semenciers pendant quelques années permet d’obtenir une régénération réussie sur la globalité des forêts dunaires, grâce à l’apport pluriannuel de graines mais aussi à travers les modifications du microclimat sous leur canopée. Contrôler la végétation spontanée afin de réduire la compétition avec les plantules de pin, et augmenter les plans de chasse afin de réduire la pression des herbivores sur les plantules, doit aussi être envisagé dans les secteurs où les échecs de régénération sont fréquents
In south-western France, the coastal fringe with maritime pine (Pinus pinaster) forest has a multifunctional role, with erosion protection, preservation of biodiversity, tourism, and wood production as main objectives. Natural regeneration is used to renew these stands after clear-cutting. However, in recent years, regeneration failures have increased in some areas,leading to significant economic losses.The objective of this work was to identify the ecological mechanisms involved in these recurrent failures, in order to propose adapted forestry management practices to ensure forest regeneration. To do this, we studied four stages of the regeneration process: seed dispersal, germination, survival, and growth. A monitoring network of five sites along the Aquitaine Coast was also used to quantify the regeneration and characterize local differences in terms of forest management practices (clear-cut vs seed-tree regeneration,and sowing vs no sowing). Two experimental sites were set up to study in detail some factors potentially important in our context (climate, plant-plant interactions, herbivory).Our results confirm that natural regeneration is a complex process, influenced by many –often interacting – environmental and management factors. The quantity of seeds reaching the forest soil does not seem to be limiting. Seed germination is strongly related to soil moisture, and is influenced by the heterogeneity of the micro topography. Summer drought, the main cause of seedling mortality, may be mitigated by remaining seed trees on the stand.Direct and indirect biotic interactions with understorey vegetation have a strong impact on seedling survival, but vary greatly both in direction and intensity, depending on the seasonand the year.Even though our results provide a better understanding of the mechanisms involved in there generation cycle of maritime pine, it is difficult to put forward a single factor explaining local regeneration failures. However, overall, maintaining seed trees for a few years allows obtaining a successful regeneration in the entire coastal forest, thanks to the multi-yearsupply of seeds but also through the modifications of the microclimate under their canopy. Controlling understorey vegetation to reduce competition with pine seedlings and increasing hunting plans to reduce herbivory pressure on seedlings should also be considered in areas where regeneration failures are common

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Rivest, Sébastien. "Variations altitudinales des interactions biotiques et de la phénologie de la floraison chez deux plantes de sous-étage de l'est de l'Amérique du Nord." Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10593.

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Un grand nombre d’espèces ont déjà subi des changements phénologiques ou des déplacements de leurs distributions en réponse aux changements anthropogéniques du climat. Comprendre comment les espèces vont réagir aux changements climatiques représente toutefois une tâche complexe puisqu’il existe une grande variabilité dans ces réponses. Cette variabilité peut être attribuée au fait que plusieurs facteurs influencent les réponses des espèces aux changements climatiques et que ces facteurs varient eux-mêmes spatialement. Dans ce mémoire, l’intensité d’interactions biotiques, soit la pollinisation et l’herbivorie, ainsi que la phénologie de la floraison sont comparées le long d’un gradient altitudinal menant à la limite de distribution altitudinale pour deux plantes de sous-étage, Erythronium americanum et Trillium erectum. Je teste en premier lieu si l’intensité de l’herbivorie et de la limitation pollinique augmentent à la limite de distribution altitudinale des espèces. Si cela est le cas, ces interactions peuvent limiter ces distributions et ainsi, le potentiel des espèces à déplacer leurs distributions face aux changements climatiques. Les résultats démontrent une augmentation de l’herbivorie et de la limitation pollinique à la limite de distribution altitudinale de T. erectum. Toutefois, la limitation pollinique devrait avoir un effet minime sur la limite de distribution altitudinale de cette espèce puisque le succès reproducteur des plantes est très peu diminué à cette limite. En se basant sur des études antérieures, la proportion d’herbivorie subie à proximité de la limite de distribution altitudinale devrait avoir des effets démographiques considérables et devrait ainsi affecter cette limite. Concernant E. americanum, l’herbivorie et la limitation pollinique sont restés constants et de faible intensité le long du gradient altitudinal. Ensuite, en disposant de quatre années de données de la phénologie de la floraison le long du gradient altitudinal étudié, je vérifie de façon préliminaire si le potentiel de flux génique est affecté par la date d’initiation du printemps, ce dernier se produisant plus hâtivement en réponse aux changements climatiques. Les résultats démontrent une diminution de l’écart temporel entre les pics de floraison des populations d’altitudes différentes lors d’années aux printemps plus hâtifs, ce qui indique une différence interpopulationnelle dans la réactivité phénologique. Toutefois, cette différence temporelle n’a pas entraîné une diminution du potentiel de flux génique. Je présente également une nouvelle méthode de mesure du potentiel de flux génique qui permet d’estimer plus efficacement ce dernier à partir de la phénologie comparativement aux méthodes actuellement utilisées.

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Nascimento, Elynton Alves do. "História natural e ecologia da interação entre Chamaecrista debilis (Vogel) Irwin & Barneby (Caesalpiniaceae), herbívoros e formigas visitantes de nectários extraflorais no cerrado." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/59/59131/tde-10072007-105422/.

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Neste estudo foi avaliado o grau de proteção conferido à Chamaecrista debilis a partir das formigas visitantes dos seus nectários extraflorais (NEFs), que são estruturas não envolvidas diretamente na polinização e que representam uma importante fonte alimentar para vários grupos de artrópodes. Foram utilizados dois experimentos, no primeiro foram escolhidas e marcadas 20 plantas, sendo 10 destinadas ao controle, permanecendo em seu estado natural, e outras 10 denominadas tratamento, onde as formigas presentes foram retiradas, sendo aplicada uma resina na base do caule, afim de impedir o acesso das formigas à planta. Em cada planta de ambos os grupos, foram marcadas 6 folhas, contando¬se seus folíolos para acompanhar a herbivoria. No segundo experimento, foram escolhidas 6 plantas, sendo marcados dois ramos em cada uma, um destinado ao controle e outro destinado ao tratamento, onde foi aplicada a resina em sua base e as formigas foram excluídas. Foram marcadas 3 folhas em cada ramo, sendo contado o número de folíolos para acompanhar a herbivoria. No primeiro experimento não objetivou¬se determinar a defesa diferencial, dependendo das espécies das formigas associadas aos NEFs, enquanto que no segundo experimento foi avaliada especificamente a defesa conferida por Camponotus cingulatus. A fenologia foi acompanhada quinzenalmente, avaliando¬se a porcentagem das estruturas da plantas. Formigas, visitantes florais, herbívoros e outros insetos presentes na planta foram coletados. Foram encontradas 15 espécies de formigas associadas aos NEFs da planta, enquanto que os principais herbívoros foram os proscopídeos (Orthoptera). Quinze espécies de visitantes florais foram relatadas, e vários outros grupos estiveram associados à planta, especialmente em relação às galhas. Os resultados dos experimentos demonstraram que a presença das formigas determina uma redução significativa da herbivoria em Ch. debilis, nos dois experimentos, sendo que esta defesa amplia¬se com o passar do tempo. Todavia, este mutualismo parece ser facultativo, como a maioria destas relações envolvendo plantas com NEFs e organismos associados.
In this study was valued the protection degree provided to Chamaecrista debilis from ants visiting its extrafloral nectaries (EFNs), that are structures not involved directly to pollination and that are a important food resource to various arthropod groups. Were performes two experiments, in the first one were choosed and marked 20 plants, where 10 were control plants, remaining in to their natural conditions, and the other 10, labeled as treatement, where the ants presents were excluded and applied a resin at the basis of the stem, to prevent the access of the ants. In wich plant of both groups were marked 6 leaves, counting the number of folioles to value the herbivory rates. In the second experiment was choosen six plants, where were marked two branches, one destined to control and the other one to the treatment, where the resin was applied at the basis, to prevent the ants? access to these branches, from where the ants were excluded. Were marked 3 leaves in wich branch counting the number of folioles to value the herbivory rates. In the first experiment was not evalueted the differencial degree of protection, depending on the ants? species while in the second one was valueted specifically the defense from Camponotus cingulatus. The phenology was evalueted each 15 days, considering the porcentage of the plants? structures. Ants, flower visitors, herbivores and other insects presents on the plant were colected. Was found 15 ant species associated to EFNs, while the main herbivore were the Proscopiidae. Fifteen specis of flower visitors were recorded and another various groups were associeted to plant, specially to the galls. The results of the two experiments showed that the presence of ants provide a significative reduce to herbivory rates in Ch. debilis, and this defense grows along the time. However, this mutualism seems to be facultative, like the majotity of these relationships involving EFN plants and associated organisms.

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Vourc'h, Gwenaël. "Interactions entre plantes longévives et grands mammifères : défense chimique du thuya géant et herbivorie par le cerf-à-queue-noire en Colombie Britannique (Canada)." Montpellier 2, 2001. http://www.theses.fr/2001MON20189.

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Pizzi, Marcello Bontempi 1988. "Perdas de produtividade de 12 clones de eucalipto submetidos a desfolhas artificiais sucessivas /." Botucatu, 2016. http://hdl.handle.net/11449/144286.

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Orientador: José Luiz Stape
Banca: Iraê Amaral Guerrini
Banca: Clayton Alcarde Alvares
Resumo: A produtividade de plantios de eucalipto no Brasil foi triplicada nas últimas quatro décadas graças, principalmente, à pesquisa intensiva, investimentos em tecnologia silvicultural, clonagem e melhoramento genético. Atualmente, existem diversas pesquisas relacionadas ao gênero Eucalyptus, mas são poucas as que abordam o tema estresse biótico por ser uma avaliação complexa e de difícil planejamento e execução. Em Piracicaba, em um sítio experimental com alta sanidade e sobrevivência, foram induzidas uma, duas e três desfolhas sucessivas, retirando-se manualmente todas as folhas da copa das árvores de 12 clones de eucalipto de extrema relevância à silvicultura brasileira. As desfolhas ocorreram aproximadamente aos 15, 19 e 23 meses de idade das árvores, e a avaliação final de perda de produtividade ocorreu aos 27 meses. O crescimento das árvores foi monitorado semanalmente, sendo possível ver o efeito das desfolhas ao longo do período. Os clones de eucalipto escolhidos para este estudo, apesar de pertencerem ao mesmo gênero, mostraram resultados bastante diferentes. O impacto das desfolhas no crescimento das árvores foi imediato e prolongado, com o crescimento próximo à zero por 50 a 120 dias após a desfolha. As desfolhas causaram redução de crescimento em DAP (Diâmetro à Altura do Peito), altura total, volume e biomassa de madeira. As árvores não desfolhadas acabaram dominando as desfolhadas. Isso causou o estiolamento das árvores desfolhadas e a redução da homogeneidade das ...
Abstract: The Brazilian Eucalyptus productivity has tripled in the last four decades, mainly because of intensive research, development of forestry and genetics. Nowadays, there are several studies related to the Eucalyptus genus, but only a few address biotic stress, as the subject is of complex evaluation, difficult planning and execution. In Piracicaba, in an experimental site with high health and survival rate, one, two and three successive defoliations were induced, manually removing all the canopy leaves of 12 extremely relevant clones to Brazilian forestry. The defoliations occurred in approximately 15, 19 and 23 months after planting and the final evaluation of productivity occurred at 27 months. Tree growth was weekly monitored, and the effect of defoliation over time was visible. The eucalypts clones chosen for this study, despite belonging to the same genus, showed quite different results. The impact of canopy defoliation on tree growth was immediate and prolonged, with growth close to zero for 50 to 120 days following defoliation. Defoliation caused growth reduction in DBH (Diameter at Breast Height), total height, volume and wood biomass. Defoliated trees were etiolated as the non-defoliated were the dominant trees in the plot. Defoliation reduced plot homogeneity. One year after the first defoliation, the 27-month-old trees that have undergone one defoliation showed 48% lower wood biomass, in comparison with non-defoliated trees (ranging from 24 to 57% by clones). ...
Mestre

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Pinto, Yuriko Yanagizawa de Almeida Nogueira. "Herbivoria em Erechtites valerinaefolia DC. (Asteraceae) : distribuição de ataque dos herbivoros e respostas compensatorias da planta." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316014.

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Orientador: João Vasconcellos Neto
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: As interações entre Erechtites valerianaefolia De. (Asteraceae) e herbívoros a ela associados foram estudadas de julho de 1991 a maio de 1993, na Serra do Japi, Jundiaí, SP, e de julho de 1992 a maio de 1993 na Fazenda Lageado, Botucatu, SP. Os principais objetivos foram testar as hipóteses que versam sobre a preferência dos herbívoros quanto ao tipo de plantas dentro de uma mesma população vegetal (Hipótese da Planta Vigorosa e Hipótese da Planta Estressada) e sobre as respostas compensatórias das plantas mediante impacto da herbivoria (Hipóteses das Respostas Sub-compensatórias, Equivalentes e Sobre compensatórias). Foi utilizada uma parcela única em cada localidade para a monitorização dos organismos a fim de descrever a fenologia, longevidade e as relações entre plantas e seus herbívoros. Parâmetros biométricos como altura, número de ramos, de folhas, de estruturas reprodutivas, área foliar e peso seco do caule, da folha e de estruturas reprodutivas foram analisados para avaliação do tamanho e do esforço reprodutivo de plantas coletadas sempre no início da fase de dispersão de sementes. E. valerianaefolia possui uma série de características que favorecem o ataque por adultos e larvas endógenas de Agatomerus signatus KIug, 1824 (Megalopodinae, Chrysomelidae) e de um forrageador de meristemas apicais não identificado. As duas espécies de herbívoros partilham o recurso atacando, o primeiro, exclusivamente plantas em reprodução e, o outro, exclusivamente plantas na fase vegetativa. Na presença das larvas brocadoras de megalopodíneos, os tecidos-alvos em tomo do túnel modificam-se, tornando-se ricos em grãos de amido. A probabilidade de ataque aumentou para plantas maiores, especialmente com relação a megalopodíneos. Plantas atacadas associaram-se a locais mais favoráveis para o crescimento e exibiram um esforço reprodutivo equivalente ou maior que plantas não são atacadas. Os dados deste trabalho apóiam integralmente a Hipótese da Planta Vigorosa e parciahnente a Hipótese do Gradiente de Respostas Compensatória pois refuta a Sub compensação
Abstract: The interactions between Erechtites valerianaefolia De. (Asteraceae) and their associated herbivores have been studied Irom July 1991 to May 1993 in Serra do Japi Jundiaí, SP, and Irom Ju1y 1992 to May 1993 in Fazenda Lageado, Botucatu, SP. The main objectives of this study were to test the hypothesis that account for the herbivores preference concerning the vigor of the host plants (The Vigorous Plant Hypothesis and The Stressed Plant Hypothesis) and the Compensatory Responses of the host plants (Undercompensatory, Equivalent and Overcompensatory Hypothesis). A single parcel in each locality was used for monitoring the organisms in order to describe the phenology, longevity and relationships between plants and their herbivores. Biometrical pararneters such as height, nwnber of branches, number of leaves, number of reproductive structures, foliar area and dry weight of the stem, leaves and reproductive structures were analysed to evaluate the size and reproductive effort of plants collected in early dispersion. E. valerianaefolia has a number of characteristics that favour the attack of adults and I.. endogenous larvas of Agatomerus signatus KIug, 1824 (Megalopodinae, Chrysomelidae) and of an non identified apical meristem forager. Both groups of herbivores share the resource, the first attacking exclusively reproducing plants and the other attacking I3exclusively plants on the vegetative stage. In the presence of the megalopodineous borers, the target tissues around the tunnel suffer a modification to become rich in starch grains. The attack probability is larger for the more vigorous plants, specially with regard to megalopodineous. The attacked plants replace the 10st tissues and can also increase their reproductive effort. These plants had been usually associated with sites that were more suitable to the growth, within the studied parcels, in both 10ca1ities. The data support The Vigorous Plant Hypothesis and the Compensatory Reactions Gradiente but reject the Undercompensation. Therefore, a fitness reduction due to herbivory in the E. va/erianaefo/ia populations was not found
Doutorado
Doutor em Ecologia

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Vieira, Christophe. "Lobophora : biotic interactions and diversification." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066195.

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L'algue brune Lobophora représente une composante benthique importante au sein des récifs coralliens tropicaux, et a à attirer dès le début des années 80 l'attention des écologistes marins en proliférant de façon remarquable au détriment des coraux. Les écologistes marins ne s’accordent toujours pas pour conclure si le changement de communauté au profit des macroalgues représente une conséquence ou une cause de la dégradation des coraux. Alors que Lobophora a fait l'objet d'observations contradictoires en termes de susceptibilité à l’herbivorie et des effets sur les coraux, les preuves suggèrent que sa prolifération dans les récifs coralliens est opportuniste et symptomatique de la dégradation des récifs. Taxonomiquement, Lobophora ne représentait que 11 espèces décrites au début de cette étude, et pratiquement toutes les espèces de Lobophora rapportées dans le monde avaient été assignées à L. variegata, décrite dans les Caraïbes. Cette étude vise à apporter un nouvel éclairage taxonomique et écologique sur ce taxon algal sujet de controverses écologiques. En utilisant une approche taxonomique basée sur l'ADN nous avons réévalué la diversité des espèces de ce genre en Nouvelle-Calédonie et au niveau mondial. Les résultats dévoilent une remarquable diversité, multipliant par 10 le nombre d’espèces jusque là reconnues. Nous avons testé si les différentes espèces de Lobophora étaient chimiquement différentes et si elles variaient (1) en toxicité envers différents coraux, et (2) en susceptibilité aux herbivores. Nous avons montré que le genre Lobophora était intrinsèquement capable de blanchir certains coraux, et nous avons isolé trois nouveaux alcools polyinsaturés C21 nommés lobophorenols A-C avec des propriétés de blanchissement. Néanmoins, les observations in situ en Nouvelle-Calédonie indiquent que, bien qu’elles soient potentiellement armées au plan chimique, les espèces de Lobophora n’induisent pas ou rarement le blanchissement de leurs hôtes coralliens, soulevant ainsi la question de l'emplacement de ces composants bioactifs dans l’algue et des facteurs environnementaux permettant leur libération supposée. Nous avons également montré que les herbivores consomment indistinctement les espèces de Lobophora. D’après ces résultats nous pouvons conclure que : (1) au sein de récifs en bonne santé, les coraux et les Lobophora maintiennent un statu quo résultant probablement d’une médiation chimique ; (2) la défense chimique ne dissuade apparemment pas le broutage des Lobophora par les principaux herbivores ; (3) il est probable que Lobophora échappe au broutage en se développant par exemple entre les branches des coraux. Le genre Lobophora représente un excellent modèle pour étudier le rôle de la spéciation écologique des algues au sein des récifs coralliens. Aussi, les études futures devront étudier le rôle des métabolites secondaires des Lobophora et enquêter sur les facteurs écologiques responsables de la diversification impressionnante de cette algue
The brown alga Lobophora represents a notable benthic component in tropical coral reefs, and began drawing the attention of marine ecologists by achieving impressive blooms at the expense of corals since the early 80s. Marine ecologists are still debating whether or not macroalgal dominance represents a consequence or cause of coral degradation. While Lobophora has been the object of contradictory observations in terms of susceptibility to herbivory and effects on corals, evidence tends to suggest that episodes of reef take-over are opportunistic and symptomatic of reef degradation. From a taxonomic point of view, only 11 species of Lobophora were recognized at the beginning of this study, and virtually all species of Lobophora reported around the world had been assigned to L. variegata, originally described from the Caribbean. This study intends to shed new taxonomical and ecological insights on this algal taxon. Using a DNA-based taxonomical approach we reassessed the species diversity of this genus at a local scale in New Caledonia and subsequently on a global level. Results disclosed a remarkable global diversity, increasing our taxonomic knowledge of this genus by no less than 10 folds. From an ecological perspective, we tested if different species of Lobophora were differentially (1) capable of chemically damaging scleractinian corals, and (2) susceptible to herbivory. We showed that the genus Lobophora was inherently capable of bleaching certain coral species, and we isolated three new C21 polyunsaturated alcohols named lobophorenols A-C with bleaching properties. Nevertheless, in situ observations in New Caledonia indicated that although potentially chemically armed, Lobophora species did not or rarely bleached their coral hosts, thereby raising the issue of the location of these bioactive components and the environmental factors enabling their putative release by the alga. We also showed that herbivores indiscriminately consumed Lobophora species. From the results of allelopathic bioassays and grazing experiments we conclude that: (1) corals and Lobophora maintain a chemical-mediated status quo on healthy reefs; (2) chemical defense apparently does not deter grazing of Lobophora by prominent herbivores; (3) it is more likely that Lobophora avoids being grazed by escape strategies such as growing under the coral canopy. The genus Lobophora represents an excellent model to study the role of ecological speciation in macroalgae within coral reefs. Therefore, future studies should be targeted at investigating the role of Lobophora secondary metabolites and exploring the ecological factors responsible for the impressive diversification of this alga

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Almeida, Cauê Guion de [UNESP]. "Crescimento e digestibilidade de dietas com diferentes teores de fibra para a tartaruga-da-Amazônia - Podocnemis expansa." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/100177.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Universidade Estadual Paulista (UNESP)
Com base no hábito alimentar da espécie, no potencial dos quelônios em utilizar matéria vegetal e na importância da fibra e de seus constituintes para alimentação animal, esta pesquisa estudou o crescimento da tartaruga-da-Amazônia (Podocnemis expansa), a disponibilidade de minerais e a digestibilidade dos nutrientes em dietas com diferentes teores de fibra bruta. Os estudos foram realizados na Universidade Estadual Paulista (UNESP), entre maio e novembro de 2008, com duração de sete meses, utilizando 160 exemplares de tartaruga-da-Amazônia provenientes do município de Ribeirão Cascalheira, região do Rio das Mortes/MT, Brasil. O aumento nos teores de fibra na dieta até 16% melhorou o crescimento da tartaruga-da-Amazônia, onde as características de crescimento apresentaram os maiores valores. Entre 16 a 20% de fibra na dieta o crescimento das tartarugas diminuiu. O maior crescimento se deu com teores semelhantes aos encontrados na dieta natural da espécie, reforçando seu potencial para utilização de dieta herbívora. A disponibilidade de minerais e a digestibilidade dos nutrientes foram influenciadas pelos teores de fibra na dieta. A tartaruga-da-Amazônia apresenta elevado potencial de digestão da fibra dietética, comparável ao de ruminantes e outros répteis herbívoros, com sua digestibilidade aumentando com o aumento do teor de fibra na dieta
Taking in consideration the potential the chelonians have for using vegetal matter and based on the eating habit of the specie and on the importance of fiber and its constituents for animal feeding, the present study aimed at evaluating the growth of the Arrau sideneck turtle (Podocnemis expansa) fed with diets of different contents of crude fiber and the availability of minerals and the digestibility of nutrients. This study was carried out Universidade Estadual Paulista (UNESP), between the months of May and November, 2008, and lasted seven months. The turtles used were 160 specimens of the Arrau sideneck turtle from Projeto Quelônios da Amazônia, State of Mato Grosso. The increase in the contents of fiber in the diet up to 16% improved the Arrau sideneck turtle’s growth, when the growth characteristics showed their best values. In diets including 20% of fiber, the turtle’s growth decreased. In diets including between 16 and 20% of fiber, the turtle’s growth decreased. The highest rate occurred when using contents similar to those found in the natural diet of the species, corroborating its potential to use herbivore diet. The availability of minerals and the digestibility of nutrients were influenced by the contents of fiber in the diet. The Arrau sideneck turtle presents a high potential for dietary fiber digestion, comparable to that of the ruminants and other herbivore reptiles, with its digestibility increasing as the contents of fiber increase

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Gadéa, Alice. "Lichens et gastéropodes du Subantartique : écologie chimique et relations trophiques." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B041/document.

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Les interactions « lichen-lichénophage » sont médiées par la présence de métabolites au sein des lichens qui peuvent influer sur les préférences alimentaires des lichénophages. Dans le contexte environnemental du Subantarctique, à faible biodiversité animale et « végétale », une étonnante richesse lichénique a contribué au succès de l’unique Gastéropode terrestre endémique, Notodiscus hookeri. Pour mieux comprendre les mécanismes en jeu, nous avons analysé les préférences alimentaires de cet escargot lichénophage et tenté de cibler les traits-clés des lichens qui modulent l’interaction trophique. À partir d’observations et de prélèvements réalisés sur l’île de la Possession (Archipel Crozet, Terres Australes et Antarctiques Françaises), deux étapes décisives de l’interaction ont été étudiées : (i) le comportement alimentaire de l’escargot en situation de choix nutritionnel, (ii) sa réponse gustative face à des métabolites en situation de non choix. Le broutage préférentiel de certaines parties de lichen a été confronté à l’analyse de la combinaison entre la teneur des métabolites secondaires et celle des métabolites primaires. La localisation des métabolites au sein du thalle de trois espèces lichéniques fréquentes sur l’île et consommées par l’escargot (Argopsis friesiana, Pseudocyphellaria crocata et Usnea taylorii) a été effectuée par l’intermédiaire de techniques chromatographiques et spectrométriques (LC-DAD-MS, GC-MS, microdissection couplée à la LC-DAD-MS, DART-MS) ainsi que par des techniques d’imagerie couplées à la spectrométrie de masse ((MA)LDI-MS). N. hookeri se révèle être une espèce généraliste et opportuniste qui se nourrit de la majorité des lichens auxquels il est confronté. Cependant, il opère des choix en se nourrissant des parties ayant une valeur nutritive élevée et ce, en dépit de la présence de métabolites secondaires potentiellement répulsifs. Plusieurs mécanismes permettant à l’escargot de contrer la toxicité de certains métabolites ont également été décrits dans ce travail. Les choix alimentaires de N. hookeri s’avèrent par conséquent répondre à un compromis entre le bénéfice d’absorption de métabolites appétents à forte valeur nutritive et le coût physiologique (détoxication, clivage, excrétion) engendré par l’ingestion de métabolites répulsifs. En conclusion, trois paramètres-clés au moins seraient à prendre en compte lors des futures études d’interactions entre lichens et lichénophages : il s’agit de la nature et de la teneur des métabolites secondaires, de la teneur en azote ainsi que de la quantité de sucres et de polyols. Les techniques d’imagerie ont fourni une voie nouvelle et prometteuse pour cibler les dégâts opérés par un phytophage. En effet, cette approche permet de mieux apprécier la distribution hétérogène au sein du thalle entre les métabolites. Pour cet escargot terrestre, les ratios de composés « appétents/inappétents » semblent jouer un rôle majeur dans la sélection de nourriture
Lichen-lichenivore interactions are mediated by the presence of metabolites in lichens, which may impact lichenivore food preferences. In the environmental context of the Subantarctic, with a low animal and “plant” biodiversity, the surprising lichen flora contributed to the success of a the only endemic subantarctic land Gastropod, Notodiscus hookeri. To better understand the snail-lichen interactions, we analyzed the food preferences of this lichenivore snail and tried to pinpoint key lichen traits modulating the trophic interaction. From observations and samplings realized on Possession Island (Crozet Archipelago, Terres Australes et Antarctiques Françaises), two decisive stages of the interaction were studied: (i) the snail feeding behavior in situation of nutritional choice, (ii) its gustatory response when facing isolated metabolites in no-choice situations. Preferential grazing of some lichen parts was linked to both secondary and primary metabolites concentrations. Intrathalline localization of metabolites was performed in three lichen species consumed by the snail and widespread on Possession Island (Argopsis friesiana, Pseudocyphellaria crocata and Usnea taylorii), using chromatographic and spectrometric techniques (LC-DAD-MS, GC-MS, microdissection coupled to LC-DAD-MS, DART-MS) and imaging mass spectrometry ((MA)LDI-MS). N. hookeri appears to be a generalist and opportunistic gastropod, feeding on most lichen species encountered. However, it is able to discriminate between lichen parts, preferentially grazing on parts with the highest nutrient value, in spite of the presence of potential deterrent secondary metabolites. We described several mechanisms helping snails to overcome the toxicity of some lichen metabolites. Snail feeding choices result in trade-off between benefits of absorbing appetent metabolites of high nutritive value and the cost of physiological processes (detoxification, cleavage and excretion) caused by the ingestion of deterrent metabolites. To conclude, three main key parameters might be relevant in future to study the interactions between lichens and lichenivores. They correspond to the nature, the histolocalisation and the content of secondary metabolites balanced by the amount of nitrogen along with sugars and polyols. Imaging techniques have provided a new and promising way to visualize the heterogeneous distribution within the thallus between these metabolites. The ratios of appetent/non appetent compounds are likely to play a major role in food selection by this land snail

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Castagneyrol, Bastien. "Rôles fonctionels et structurels de la biodiversité sur les comunautés d'insectes et d'herbivorie associée : une approche expérimentale." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14558/document.

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Les relations entre plantes et herbivores occupent une part importante des travaux concernant le rôle de la biodiversité dans le fonctionnement des écosystèmes. Les effets de la diversité des plantes sur les herbivores et la phytophagie se répartissent le long d’un continuum entre résistance et susceptibilité par association, ces deux concepts décrivant respectivement la réduction ou au contraire l’augmentation des dégâts causés par les herbivores avec la diversité des plantes dans les communautés végétales. Si de nombreux travaux menés dans différents écosystèmes suggèrent que la résistance par association est plus fréquente que la susceptibilité par association, les mécanismes sous jacents restent discutés et semblent dépendre de la plus ou moins grande spécialisation des herbivores et de l’identité des espèces végétales associées. En particulier deux questions se posent : (1) quel est l’effet de la diversité des plantes sur la diversité des insectes, et principalement sur les insectes herbivores ? (2) Quelle composante de la diversité des plantes explique le mieux la résistance et la susceptibilité par association ? La méta-analyse présentée dans cette thèse montre que la diversité des animaux augmente avec la diversité des plantes, quels que soient les écosystèmes et les taxons considérés. Dans le cas des Arthropodes, la richesse spécifique des herbivores est mieux corrélée à la richesse spécifique des plantes que celle des prédateurs. De plus, la diversité des herbivores augmente plus rapidement que la diversité des prédateurs avec la diversité des plantes. Ces observations soulèvent un paradoxe : si la diversité des herbivores augmente avec celle des plantes, comment expliquer les nombreux cas où la phytophagie diminue (résistance par association) ? Cette question a fait l’objet d’une approche expérimentale centrée sur le chêne pédonculé et fondée sur la manipulation de la diversité spécifique et génétique des essences forestières. Il en ressort que ces deux niveaux de diversité ont des effets contrastés sur la phytophagie. Les dégâts causés par les insectes herbivores généralistes tendent à augmenter avec la diversité génétique chez leur hôte (susceptibilité par association), alors que les spécialistes ne répondent pas à la diversité génétique chez le chêne. Au contraire, la diversité spécifique est à l’origine d’une résistance par association pour les herbivores spécialistes mais elle est sans effet sur les généralistes. Un résultat original émerge des travaux présentés dans cette thèse : les effets de la diversité des plantes sur les insectes herbivores et leurs dégâts s’exprimeraient principalement à l’échelle locale – celle d’un arbre et de ses voisins immédiats – au travers de « l’apparence » des arbres, une variable conditionnée par leur taille et celle de leurs voisins. La prise en compte de la spécialisation des insectes herbivores et des différentes composantes de la diversité des arbres contribue donc à une meilleure compréhension des mécanismes impliqués dans la résistance et la susceptibilité par association des forêts mélangées
Functional and structural consequences of plant diversity on insect communities and herbivoryThe relationship between biodiversity and ecosystem functioning remains a key issue in ecology. In particular it has been suggested that plant species diversity can trigger plant-insect interactions, ranging from associational resistance (higher herbivory in monocultures than in more diverse plant communities) to associational susceptibility (higher herbivory in plant mixtures). Although it is now widely acknowledged that associational resistance is more frequent than associational susceptibility, the underlying mechanisms are still debated and seem to depend on herbivore specialization and plant species identity. To contribute to this debate we addressed two questions: (1) What are the consequences of plant diversity for insect herbivore diversity? (2) Which component of plant diversity better accounts for herbivory? On the basis of a meta-analysis we show in this report that animal diversity significantly increase with increasing plant diversity, regardless of habitats or taxa. In arthropods, herbivores species richness increases more steeply with plant richness than predator richness. This result raises an apparent paradox: if herbivore diversity is positively correlated with plant diversity, why herbivory decreases with increasing plant diversity (associational resistance)? To solve this paradox we developed an experimental approach focused on pedunculate oak and based on the manipulation of tree genetic and species diversity. We showed that generalist and specialist herbivores respond differently to the two levels of tree diversity. Herbivory by generalist herbivores significantly increased with oak genetic diversity (i.e. associational susceptibility) while specialist herbivores did not respond to the genetic diversity of their host tree. Conversely, tree species diversity triggered associational resistance to specialist insect herbivores but had no effect on generalists. The novelty of this works also lies in the identification of a new mechanism that may account for associational resistance in tree species mixtures: host apparency. More apparent oak trees – those that are taller than their neighbours – are more prone to insect damage. Increasing tree species diversity comes together with higher probability of associating faster growing species (such as pine or birch) than can hide neighbouring oaks, reducing their apparency and then their susceptibility. Our findings suggest that accounting for the diet breadth of insect herbivores and the different components of tree diversity can contribute to a better understanding of the mechanisms leading to associational resistance or susceptibility in mixed forests

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Gianni, Fabrizio. "Conservation et restauration écologique des forêts marines Méditerranéennes." Thesis, Nice, 2016. http://www.theses.fr/2016NICE4028/document.

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Une perte des forêts marines de grandes algues brunes a été observée dans les récentes décennies, causant un changement des écosystèmes et une réduction de la biodiversité. Dans le cadre du projet MMMPA, ce travail de thèse vise à répondre à certaines importantes questions liées à la conservation et à la restauration des forêts d'algues, au rôle des Aires Marines Protégées (AMPs) et les poissons herbivores. Les résultats des expériences sur le terrain ont montré que les poissons herbivores indigènes, probablement Salpa Sarpa (saupes), peuvent être les herbivores les plus efficace des ceintures intertidales de Cystoseira. En effet, les saupes affectent fortement la croissance, la biomasse et la reproduction des forêts naturelles et limitent le succès de la restauration sur des substrats artificiels. Le rôle des poissons herbivores a probablement été négligé dans la régulation des communautés macroalgales Méditerranéennes. Une revue de la littérature existante a montré une amélioration de l'intérêt scientifique (articles publiés) sur les espèces formant les forêts marines, au cours des dernières décennies. Cependant, la plupart de la recherche scientifique n’est pas en relation avec les AMPs, probablement parce que les forêts marines ne sont pas toujours considérées pendant la création des AMPs et dans les plans de gestion. Les études sur les forêts marines étant concentrée dans les pays développés, elles ne sont pas réparties de manière homogène dans le monde
Loss of marine forests of large brown seaweeds has been observed in recent decades, causing a reduction of ecosystem biodiversity. In the framework of the MMMPA project, this PhD aimed to address some important topics related to the conservation and restoration of algal forests, the role of Marine Protected Areas (MPAs) and fish herbivory. Different approaches were used: macroalgae surveys, literature reviews, manipulative experiments, tank-based experiments and GIS habitat mapping. Results from field experiments showed that native herbivorous fish, likely Sarpa salpa (salemas), can be the most effective herbivore of intertidal Cystoseira belts both on natural and artificial substrates. Indeed, salemas strongly affected the growth, biomass and reproductive output of natural forests and limited restoration success on artificial substrates. Likely, the role of the herbivorous fish in structuring macroalgal communities has been overlooked in the Mediterranean Sea so far. A review of the existing literature showed that knowledge on marine forests forming species has improved in recent decades. However, most of the research is not in relation to MPAs, likely due to the fact that marine forests are not always included in MPAs planning and management plans. Studies on marine forests are not homogeneously distributed in the world, being concentrated in the developed countries. Interestingly, an increase of the scientific interest (published papers) was observed. Nowadays, marine forests are under continuous threats and especially sensitive to multiple impacts

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Veiga, Kelen Rodrigues da. "Preferência alimentar do preá (Cavia magna Ximenez 1980), em uma ilha subtropical no sul do Brasil." reponame:Repositório Institucional da FURG, 2013. http://repositorio.furg.br/handle/1/6032.

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O gênero Cavia pertence à família Caviidae. No Rio Grande do Sul são encontradas as espécies C. aperea e C. magna, sendo a última ocorrente na Ilha dos Marinheiros, local onde foi realizado este estudo. A disponibilidade de alimentos no ambiente é importante para o desenvolvimento da espécie. Assim, o objetivo desse estudo foi determinar preferência alimentar de Cavia magna, relacionando as espécies vegetais encontradas na dieta com suas disponibilidades no ambiente. Foram realizadas sazonalmente, no período de um ano, coletas e levantamento da vegetação, estimando a cobertura de cada espécie para posteriormente calcular o Índice de valor de importância (IVI). Mensalmente, nesse mesmo período, foram coletadas amostras de fezes dos preás, para análise micro-histológica, técnica esta amplamente utilizada para determinação da dieta de herbívoros. Os dados foram coletados em dois transectos, um ao Norte e outro ao Sul da Ilha em 30 unidades amostrais de 1m², cada. Testes MANOVA e de Mantel foram realizados para determinar a relação entre a distribuição e abundância das espécies vegetais no ambiente, e as espécies encontradas nas amostras fecais. No ambiente foram registradas 96 espécies distribuídas em 44 famílias durante os períodos amostrados, sendo Asteraceae, Poaceae e Cyperaceae as mais representativas. Juncus acutus apresentou maior Índice de Valor de Importância (IVI) na área Norte nos quatro períodos estudados e no verão e outono na área Sul. Cladium jamaicense e Plantago australis tiveram maior IVI nos períodos de inverno e primavera, respectivamente. Nas amostras fecais foram identificadas 24 espécies vegetais pertencentes a 19 famílias. Poaceae foi a família com maior número de espécies frequente na dieta para ambas as áreas. Na área Norte, Hypoxis decumbens e Juncus acutus foram as espécies de maior frequência nas amostras de fezes, enquanto que na área Sul, a espécie mais frequente foi Paspaum urvillei. Os testes MANOVA demonstraram variabilidade de espécies tanto no ambiente quanto nas amostras de fezes, no que se refere às estações do ano. O teste de Mantel mostrou influência significativa entre a disponibilidade da vegetação e as espécies consumidas pelo preá, porém com baixa correlação. As espécies mais consumidas foram buscadas por C. magna em maiores distâncias, ou selecionadas, mesmo quando ofertadas em menores quantidades no ambiente, demonstrando seletividade e preferência deste roedor por algumas espécies vegetais no presente estudo.
The Genus Cavia belongs to the family Caviidae. In Rio Grande do Sul are found the species C. aperea and C. magna, the last occurring on the Marinheiros Island, where the study was conducted. The availability of food in the environment is crucial for the development of the species. The objective of this study was to determine the feeding preference of Cavia magna listing the plant species found in the diet with their availability in the environment. Were conducted seasonally, during one year, sampling and survey of vegetation, estimating the coverage of each species to subsequently calculate the importance value index (IVI). Monthly, during the same period, samples of cavies’s feces were collected for microhistological analysis, this technique is widely used to determine the diet of herbivores. Data were collected in two transects, one North and the other South of the island in 30 sampling units of 1m² each. MANOVA and Mantel’s Test was conducted to determine the relationship between the abundance and distribution in the environment of the plant species and species found in fecal samples. The environment has been recorded 96 species in 44 families in the sample periods, and Asteraceae, Poaceae and Cyperaceae were the most representative. Juncus acutus showed greater Importance Value Index (IVI) in the North area in the four periods and during summer and autumn, in the South area. Cladium jamaicense and Plantago australis had higher IVI during winter and spring, respectively. In fecal samples were identified 24 plant species belonging to 19 families. Poaceae was the family with the highest number of species in the diet for both areas. In the North, Hypoxis decumbens and Juncus acutus were the species most frequently in stool samples, while in the South, the most frequent was Paspaum urvillei. MANOVA tests demonstrate that there is both species variability in the environment and in the feces sample, with respect to seasons. The Mantel test showed significant influence between the availability of vegetation and species consumed by cavy, but with low correlation. The most consumed species were sought by C. magna at greater distances, or selected, even when offered in smaller quantities in the environment, demonstrating selectivity and preference of this rodent by some vegetal species in this study

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Pais, Mara Patrícia. "Valor Nutritivo e Investimento em Defesas em Folhas de Didymopanax vinosum E. March. e sua Relação com a Herbivoria em Três Fisionomias de Cerrado." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/59/59131/tde-13032005-181922/.

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O estudo teve por objetivo verificar se existe um gradiente de estresse nutricional entre fisionomias distintas na ARIE Pé-de-Gigante e verificar se às plantas de cerrado podem ser aplicadas (1) a hipótese da disponibilidade de recursos (Coley et al., 1985), segundo a qual plantas em ambientes com menos recursos investem mais em defesas e (2) a hipótese de que plantas sob estresse abiótico tornam-se mais susceptíveis a insetos herbívoros (Rhoades, 1979; White, 1969, 1984). Além disso, pretendeu-se verificar a composição da fauna de insetos herbívoros e de predadores e parasitóides associadas à planta. Foram comparados os padrões de herbivoria foliar, bem como a fauna de insetos herbívoros e de predadores e parasitóides associada a Didymopanax vinosum E. March. em fisionomias de campo cerrado, cerrado e cerradão, relacionando-os com possíveis variações nutritivas, da dureza foliar e dos teores de celulose, ligninas e taninos. Foi constatado que as folhas jovens de D. vinosum possuem maior conteúdo de água e nitrogênio, menor dureza e menores teores de celulose, ligninas e taninos. As análises de solo não apontaram diferenças entre as áreas em termos de composição química, indicando a ausência de um gradiente de estresse nutricional. No entanto, as plantas do cerrado e do cerradão apresentaram folhas mais ricas em água e nitrogênio e menor dureza que as plantas do campo cerrado. As plantas das duas primeiras áreas investem mais em taninos e menos em ligninas, os principais tipos de defesas quantitativas. Outros fatores abióticos podem exercer grande influência nas concentrações destes compostos, como a luminosidade, cuja deficiência parece colocar as plantas do sub-bosque do cerrado e do cerradão em situação de estresse. Desse modo, a hipótese 1 aplica-se a D. vinosum apenas quando se considera o investimento em taninos, mas não em ligninas. A herbivoria por insetos mastigadores foi muito baixa tanto em folhas jovens quanto em adultas (inferior a 2 e 5%, respectivamente). Em folhas adultas, foi maior apenas no cerradão, corroborando parcialmente a hipótese 2. Por outro lado, a herbivoria por insetos sugadores em folhas jovens foi intensa, principalmente no campo cerrado e no cerradão, sendo Lyothrips didymopanacis (Thysanoptera) a principal espécie responsável pelos danos foliares. As populações desta espécie demonstraram ser influenciadas primariamente pela disponibilidade de folhas jovens da planta. Populações de aranhas e coccinelídeos acompanharam parcialmente as flutuações das populações de L. didymopanacis.
This study aimed at verifying the existence of a nutritional stress gradient among distinct physiognomies at Pé-de-Gigante Relevant Ecological Interest Area (ARIE), and in such case, verifying whether the following hypotheses can be applied to cerrado plants: (1) the resource availability hypothesis (Coley et al., 1985), according to which plants in environments with fewer resources invest more in defence strategies, and (2) the hypothesis stating that plants under abiotic stress become more susceptible to herbivorous insects (Rhoades, 1979; White, 1969, 1984). In addition, the study also aimed at verifying the composition of the herbivorous insects fauna as well as those of predators and parasitoids associated with the plant. The leaf herbivory standards were compared and so were the faunas of herbivorous insects, predators and parasitoids associated with Didymopanax vinosum E. March in physiognomies of campo cerrado, cerrado and cerradão. Such standards were then related to possible variations in leaf nutrition, toughness and levels of cellulose, lignins and tannins. It was observed that young leaves of D. vinosum had more water and nitrogen content, less hardness and smaller levels of cellulose, lignins and tannins. Soil analyses did not show differences among the areas as to chemical composition, which indicates the absence of a nutritional stress gradient. However, cerrado and cerradão plants presented leaves with greater water and nitrogen contents as well as less toughness than campo cerrado plants. The plants in the two first areas invested more in tannins and less in lignins, which are the two major types of quantitative defences. Other abiotic factors can exert great influence on the concentration of these compounds, such as luminosity, whose deficiency seems to place cerrado and cerradão understory plants in a stressing situation. Therefore, hypothesis 1 applies to D. vinosum only when the investment in tannins is taken into account, but not that in lignins. Herbivory in chewer insects was low both in young and adult leaves (lower than 2 and 5%, respectively). As to adult leaves, it was higher only in cerradão, which partly supports hypothesis 2. On the other hand, herbivory by sucking insects on young leaves was intense, especially in campo cerrado and cerradão where Lyothrips didymopanacis (Thysanoptera) was the mainly responsible species for leaf damage. This species population showed to be primarily influenced by the availability of the plants young leaves. Populations of spiders and Coccinelideae partly followed L. didymonopacis population flows.

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Erdogmus, Graziella Diogenes Vieira Marques. "A perda de área foliar e sua relação com o gênero Ectatomma (Formicidae: Ectatomminae) em uma comunidade de cerrado." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/59/59131/tde-23042010-152733/.

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A perda de área foliar, em sua maior parte resultante da ação de herbívoros, é um dos fatores que regulam o sucesso reprodutivo de uma planta e indiretamente de todos os consumidores relacionados na comunidade. A maior parte dos estudos feitos com perda foliar e herbivoria são pontuais, ou seja, referem-se a uma ou poucas espécies vegetais. Para os cerrados, a savana tropical brasileira, a maior savana em extensão e diversidade no mundo, não há nenhum estudo que investigue a dinâmica de perda de área foliar ao longo do tempo na comunidade, considerando os fatores climáticos e fenológicos que podem influenciar este processo, além da presença dos principais predadores de herbívoros atrópodes na vegetação de cerrado, as formigas, sendo este o principal objetivo do presente estudo. O estudo foi desenvolvido em uma área de reserva de Cerrado de 628 ha, situada em Uberlândia, MG (18º59S, 48º18O), tendo os dados sido coletados de janeiro a dezembro de 2007 (bimestralmente) e de 2008 (mensalmente). Foram estabelecidos aleatoriamente na área de cerrado sensu stricto da reserva, 15 quadrantes de 10m x 10m onde todos os indivíduos com diâmetro à altura do peito igual ou superior a três centímetros foram marcados e incluídos na amostra. Em cada quadrante observou-se (sem remoção), seis folhas (escolhidas aleatoriamente duas da parte alta, duas da parte mediana e duas de ramos mais baixos), por planta de cada espécie, sendo registrada a porcentagem de área foliar perdida. Foram amostrados um total de 1006 indivíduos distribuídos em 82 espécies e 34 famílias. A espécie Ouratea spectabilis (137 indivíduos) foi a mais abundante na área de estudo, seguida de Banisteriopsis malifolia (122), Machaerium acutifolium (59) e Tabebuia ochracea (41). A perda de área foliar variou significativamente ao longo do tempo (meses) e entre as famílias e espécies de plantas. Os meses mais secos do ano apresentaram a maior perda de área foliar tanto em 2007 (abril, junho e agosto) quanto em 2008 (de maio a agosto). Os fatores climáticos influenciaram significativamente a perda de área foliar, pois ela variou ao longo do tempo. Portanto, os resultados do presente estudo indicaram que a perda de área foliar da comunidade de plantas de cerrado varia sazonalmente e ocorre com maior intensidade na estação seca. Fatores abióticos como temperatura e precipitação influenciam a fenologia das espécies de plantas, que buscam o melhor momento para maximizar seu desenvolvimento e evitar que inimigos naturais causem perdas significativas para sua sobrevivência e sucesso reprodutivo. As características de cada espécie promovem diferenças na perda de área foliar, devido às defesas e/ou associações mutualísticas que possuem. A presença de nectários extraflorais associados às formigas desempenha um papel significativo para as plantas. Dentre os fatores bióticos, a presença de ninhos de formigas Ectatomma teve um impacto positivo para as plantas reduzindo a perda de área foliar.
The loss of leaf area, mostly resulting from the action of herbivores is one of the factors that regulate the reproductive success of a plant and indirectly to all consumers connected to the community. Most studies of herbivory and leaf loss are punctual, i.e., refer to one or a few plant species. In the cerrado, a tropical savanna in Brazil, the largest savanna in scope and diversity in the world, there are no studies to investigate the dynamics of loss of leaf area over time in the community, considering the climatic factors, phenology and carnivorous ants that can influence this process, which is the main objective of this study. The study was conducted in a closed area of 628 ha of Cerrado, located in Uberlandia, Brazil (18 º 59\'S, 48 18\'W) and the data were collected from January to December 2007 (bimonthly) and 2008 (monthly). Were established randomly in the area of cerrado of the reserve, 15 quarters of 10m x 10m where all trees with diameter at breast height greater than or equal to three centimeters were marked with numbered label and sampled. In each quadrant was observed (without removal), six leaves (randomly chosen two of high part, two of the middle, and two of the lower branches), in plant species, and recorded the percentage of leaf area lost. We sampled a total of 1006 individuals belonging to 82 species and 34 families. The species Ouratea spectabilis (137 individuals) was the most abundant in the study area, followed by Banisteriopsis malifolia (122), Machaerium acutifolium (59) and Tabebuia ochracea (41). The loss of leaf area varied significantly over time (months) and between families and species of plants. The driest months of the year showed the greatest loss of leaf area in both 2007 (April, June and August) and in 2008 (May-August). Climatic factors also significantly influenced the loss of leaf area, as it varied over time, depending on the rainfall and temperature variation. Therefore, the results of this study indicated that the loss of leaf area community of cerrado plants varies seasonally and occurs mostly in the dry season. Abiotic factors like temperature and rainfall influence the phenology of species of plants, seeking the best time to maximize their development and prevent natural enemies result in significant losses for their survival and reproductive success. The characteristics of each species promote differences in leaf area loss due to defenses and / or mutualistic associations they have. The presence of extrafloral nectaries associated with ants play a significant role for plants. For this reason, among the biotic factors, the presence of Ectatomma nests had a significant positive impact on reducing the loss of leaf area, since these ants are predators of herbivores.

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Junqueira, Luis Renato [UNESP]. "Quantificação de danos causados por Thaumastocoris peregrinus (Hemiptera:Thaumastocoridae) em eucalipto." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144403.

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Introduzido no início do século XX, o eucalipto, se adaptou bem a diversos locais no Brasil, sendo hoje o gênero florestal mais plantado no país. Dentre suas inúmeras utilizações, destacam-se a produção de celulose, papel, carvão e chapas de fibras. Desde o início dos anos 2000 houve a introdução de pragas exóticas, que devido à ausência competição e controle natural e presença de alimento e clima apropriados, tornaram-se problemas para os cultivos de eucalipto. Dentre as pragas introduzidas no país, destaca-se o percevejo bronzeado do eucalipto, Thaumastocoris peregrinus. Esta espécie teve sua detecção no Brasil em 2008 e desde então já atacou mais de 500 mil hectares de florestas. Contudo, ainda não existem informações consolidadas sobre as perdas ocasionas pelo seu ataque. Os objetivos deste trabalho foram quantificar a perda em produção de madeira causada por T. peregrinus sob duas situações: (1) utilizando-se como hospedeiro um mesmo clone em duas idades diferentes e (2) utilizando-se dois clones de eucalipto distintos em uma mesma idade. Para isolar o ataque de T. peregrinus os ensaios foram conduzidos em parcelas pareadas com aplicação de calda inseticida para proteger algumas parcelas de seu ataque. Para quantificar o impacto do ataque por T. peregrinus foram contados o número de insetos em folhas e armadilhas, mensuradas o crescimento em diâmetro e altura das árvores com posterior cálculo de volume. Os resultados mostraram redução em diâmetro, altura e volume devido ao ataque de T. peregrinus, com a técnica de aplicação de inseticidas pulverizados sendo mais eficiente que o método de drench. Como conclusões a perda potencial causada por T. peregrinus levando-se em consideração apenas um pico populacional da praga foi de R$ 1,4 mil/hectare.
Introduced in the early twentieth century, eucalypt has adapted well to different locations in Brazil, being the most planted genus in the country. Among its many uses, it highlights the production of pulp, paper, coal and fiberboard. Since early 2000s the introduction of exotic pests which encountered no competition or natural enemies and presence of food and suitable climate have become pests for eucalypt plantations. Among the main pests introduced in Brazil is the bronze bug, Thaumastocoris peregrinus. Its first detection in Brazil was in 2008 and since then it has attacked more than 500 thousands hectares of eucalypt forest. However, there are no consolidated information about growth losses caused by its attack. The objectives of this study were to quantify the loss in wood production caused by T. peregrinus in two situations: (1) using as a host the same material in two different ages and (2) using two different Eucalyptus materials in the same age. To isolate T. peregrinus attack the experiment were conducted in twin plots with insecticide spraying to protect trees from T. peregrinus attack. To quantify the impact caused by T. peregrinus attack the number of insects were counted on leaves and traps, the growth on diameter and height of trees were measured for subsequent volume calculation. The results showed a reduction in diameter, height and volume due to the attack of T. peregrinus. Insecticide spraying method got better results than drench method. As conclusions the potential loss caused by T. peregrinus taking into consideration only one pest outbreak was R$ 1.400, 00/ hectare.

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Junqueira, Luís Renato 1986. "Quantificação de danos causados por Thaumastocoris peregrinus (Hemiptera:Thaumastocoridae) em eucalipto /." Botucatu, 2016. http://hdl.handle.net/11449/144403.

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Orientador: Carlos Frederico Wilcken
Banca: Leonardo Rodrugues Barbosa
Banca: Everton Pires Soliman
Resumo: Introduzido no início do século XX, o eucalipto, se adaptou bem a diversos locais no Brasil, sendo hoje o gênero florestal mais plantado no país. Dentre suas inúmeras utilizações, destacam-se a produção de celulose, papel, carvão e chapas de fibras. Desde o início dos anos 2000 houve a introdução de pragas exóticas, que devido à ausência competição e controle natural e presença de alimento e clima apropriados, tornaram-se problemas para os cultivos de eucalipto. Dentre as pragas introduzidas no país, destaca-se o percevejo bronzeado do eucalipto, Thaumastocoris peregrinus. Esta espécie teve sua detecção no Brasil em 2008 e desde então já atacou mais de 500 mil hectares de florestas. Contudo, ainda não existem informações consolidadas sobre as perdas ocasionas pelo seu ataque. Os objetivos deste trabalho foram quantificar a perda em produção de madeira causada por T. peregrinus sob duas situações: (1) utilizando-se como hospedeiro um mesmo clone em duas idades diferentes e (2) utilizando-se dois clones de eucalipto distintos em uma mesma idade. Para isolar o ataque de T. peregrinus os ensaios foram conduzidos em parcelas pareadas com aplicação de calda inseticida para proteger algumas parcelas de seu ataque. Para quantificar o impacto do ataque por T. peregrinus foram contados o número de insetos em folhas e armadilhas, mensuradas o crescimento em diâmetro e altura das árvores com posterior cálculo de volume. Os resultados mostraram redução em diâmetro, altura e volume devido ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Introduced in the early twentieth century, eucalypt has adapted well to different locations in Brazil, being the most planted genus in the country. Among its many uses, it highlights the production of pulp, paper, coal and fiberboard. Since early 2000s the introduction of exotic pests which encountered no competition or natural enemies and presence of food and suitable climate have become pests for eucalypt plantations. Among the main pests introduced in Brazil is the bronze bug, Thaumastocoris peregrinus. Its first detection in Brazil was in 2008 and since then it has attacked more than 500 thousands hectares of eucalypt forest. However, there are no consolidated information about growth losses caused by its attack. The objectives of this study were to quantify the loss in wood production caused by T. peregrinus in two situations: (1) using as a host the same material in two different ages and (2) using two different Eucalyptus materials in the same age. To isolate T. peregrinus attack the experiment were conducted in twin plots with insecticide spraying to protect trees from T. peregrinus attack. To quantify the impact caused by T. peregrinus attack the number of insects were counted on leaves and traps, the growth on diameter and height of trees were measured for subsequent volume calculation. The results showed a reduction in diameter, height and volume due to the attack of T. peregrinus. Insecticide spraying method got better results than drench method. As conclusions the potential loss caused by T. peregrinus taking ...
Mestre

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Noumi, Zouhaier. "Acacia tortilis (Forssk.) Hayne subsp. raddiana (Savi) Brenan en Tunisie pré-saharienne : structure du peuplement, réponses et effets biologiques et environnementaux." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14130/document.

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Ce travail de thèse a pour objectif principal de comprendre la dynamique de l’espèce fondatrice de l’écosystème de la région de Bled Talah, ainsi que les mécanismes susceptibles de mieux comprendre ses interactions avec la végétation compagne. Des mesures dendrométriques accomplies par des essais de détermination d’âge, ont fait ressortir que le peuplement de la forêt du Bou Hedma semble naturellement suivre plutôt une certaine dynamique régressive. C’est ainsi que nos résultats démontrent plutôt la dominance des individus de grandes circonférences (des individus âgés). Les obstacles à la faible régénération naturelle de ce taxon sont, essentiellement, l’infestation des graines par les bruches, la possibilité d’un éventuel effet autoallélopathique et la dominance des interactions négatives (compétition) entre la végétation du Parc National du Bou Hedma et les jeunes plants d’Acacia. Concernant, les interactions biotiques, nos résultats ont permis d’enrichir les débats actuels sur l’importance et la direction des interactions le long des gradients de stress et de perturbation. Une dominance des interactions négatives (compétition), le long des deux gradients a été démontrée, avec une chute de l’importance de la compétition en présence d’herbivorie. Les mesures environnementales et biologiques ont permis de conclure, qu’Acacia tortilis subsp. raddiana, a un effet globalement bénéfique pour le sol, ainsi que pour la végétation naturelle environnante. Compte tenu du rôle clef de cette espèce sous les conditions contraignantes du bioclimat aride, la nécessité de minimiser le risque de la faible régénération naturelle de ce taxon est prioritaire dans les grands programmes de reboisement et de restauration des écosystèmes arides
The main aim of this work were to understand the dynamics of the founding species of the ecosystem of the region of Bled Talah, as well as the mechanisms to understand better its interactions with the vegetation partner. Dendrometric parameters were measured for each tree then determination of age were estimated. This work improves general understanding of the factors explaining the structure of the Acacia tortilis subsp. raddiana. These species naturally seems to follow rather a certain regressive dynamics. The possible reasons for regeneration failure natural regeneration of Acacia tortilis subsp. raddiana were especially the high infestation of seeds by Bruchidius raddianae, the autoallelopathic effetcs and the dominance of the negative interactions (competition) between the vegetation of the National park of Bou Hedma and the young plantations of Acacia tree. The importance and direction of biotic interactions along environmental gradients is still a major debate in plant ecology. Through the study of biotic interactions, our results suggests the dominance of competition between nurses and target species used in this work.The results of this study confirmed the positive effect of Acacia tortilis subsp. raddiana on the understorey vegetation composition and diversity in arid ecosystems. Once, established in the dry area, this species ameliorates microclimate including soil conditions that may be suitable to the regeneration and the growth of other species. In this way, this species will provide beneficial effects to the generating seedlings in the vicinity and therfore will help rehabilitating degraded areas

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Gayet, Guillaume. "COLONISATION D'UN ECOSYSTEME D'EAU DOUCE HETEROGENE PAR UN OISEAU D'EAU HERBIVORE : LE CYGNE TUBERCULE (CYGNUS OLOR) DANS LES ETANGS PISCICOLES DE DOMBES." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2010. http://tel.archives-ouvertes.fr/tel-00723066.

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Dans certains cas, la colonisation des zones humides par les espèces animales et végétales peut être une menace majeure pour la biodiversité. Il est donc primordial de mieux connaître l‟écologie des espèces colonisatrices pour définir leurs relations avec le reste de l‟écosystème. Nous avons étudié les conséquences de la colonisation relativement récente des étangs piscicoles français par le cygne tuberculé (Cygnus olor). Nous nous sommes intéressés à l‟expression de cette colonisation dans l‟espace par l‟étude des processus de sélection de l‟habitat. Nos résultats montrent que dans un paysage d‟étangs, la répartition des cygnes tuberculés dépend à la fois de la configuration spatiale des étangs (aire - isolement), des ressources disponibles et du statut de reproduction des cygnes tuberculés. Nous avons ensuite étudié les interactions entre le cygne tuberculé et les communautés animales et végétales des étangs. Sur les sites de cantonnement des couples, nous n‟avons pas montré d‟effet de la présence des cygnes tuberculés sur l‟abondance des oiseaux d‟eau, et aucune forme d‟exclusion spatiale à l‟échelle de l‟étang. En revanche, les cygnes tuberculés peuvent générer une déplétion significative des herbiers de macrophytes aquatiques, suggérant des effets en cascade sur les autres communautés des étangs piscicoles. Comme toute perturbation générée par une espèce colonisatrice, celle associée à l‟arrivée des cygnes doit néanmoins être replacée dans le contexte plus large des régimes de perturbations à l‟oeuvre sur l‟écosystème, ce qui importe particulièrement dans le cas d‟écosystèmes aussi dépendants de l‟activité humaine que les étangs piscicoles.

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Machado, Glauco Barreto de Oliveira 1988. "Associação de anfípodes herbívoros com a alga parda Sargassum filipendula e suas epífitas : variação temporal e efeito da dieta sobre a aptidão." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315931.

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Orientadores: Fosca Pedini Pereira Leite, Silvana Gomes Leite Siqueira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Macroalgas oferecem alimento e hábitat para pequenos herbívoros, como anfípodes. O papel da macroalga como alimento é um dos principais fatores que influencia a interação herbívoro-macroalga. Dessa forma, para compreender essa interação, é imprescindível conhecer as consequências da dieta sobre a aptidão de pequenos herbívoros e a associação desses animais com as macroalgas em campo. Nesse estudo, avaliamos a variação temporal de anfípodes herbívoros da família Ampithoidae e da alga parda Sargassum filipendula e suas epífitas. Em complemento, investigamos o efeito do consumo de algas com diferentes características (Sargassum filipendula e duas algas epífitas, Dictyota cervicornis e Hypnea musciformis) sobre a aptidão de dois ampitoídeos, Cymadusa filosa e Sunampithoe pelagica, bem como a preferência e taxa alimentar desses anfípodes. A composição das espécies de Ampithoidae variou quanto ao tempo e foi influenciada pela biomassa de Sargassum e pela intensidade de epifitismo. Sunampithoe pelagica destacou-se como a espécie de ampitoídeo mais abundante, apresentando forte associação com a biomassa de Sargassum. As espécies C. filosa, Ampithoe marcuzzi e A. ramondi ocorreram em menor abundância e acompanharam a variação da biomassa de epífitas. Nos experimentos de aptidão, jovens de S. pelagica alimentados com Sargassum, em comparação àqueles nos tratamentos com Hypnea e Dictyota, apresentaram maior sobrevivência, o que sugere uma dieta restrita apresentada por essa espécie. Para C. filosa, a sobrevivência foi semelhante entre jovens submetidos às três dietas, porém, aqueles alimentados com Sargassum apresentaram maior crescimento e sucesso reprodutivo. Em um experimento de múltipla escolha de algas, adultos de C. filosa e S. pelagica apresentaram maior preferência de consumo pela alga Sargassum. Quando não oferecida escolha quanto ao alimento, as três algas foram consumidas por adultos de C. filosa a uma mesma taxa. Em contraste, Sargassum foi à alga mais consumida por adultos de S. pelagica no experimento de taxa alimentar. Apesar de ambas as espécies de anfípodes apresentarem maior preferência e sucesso ao consumirem Sargassum, elas responderam de maneiras distintas quando oferecidas outras algas, o que pode refletir as diferenças observadas entre essas espécies quanto aos seus padrões de ocorrência em campo. Nesse sentido, enquanto um importante componente na interação entre pequenos herbívoros e macroalgas, a dieta pode influenciar as respostas de anfípodes herbívoros às variações de biomassa das macroalgas. Além disso, nossos resultados reforçam a importância de se considerar as especificidades de cada herbívoro para compreensão do impacto desses animais sobre a comunidade de algas
Abstract: Macroalgae offer food and habitat for small herbivores, such as amphipods. The role of the macroalgae as food is one of the main driving factors of the herbivore-macroalga interaction. Hence, in order to comprehend this interaction, one must necessarily know the consequences of the diet on the fitness of small herbivores and on the association between these animals and the algae in the field. We herein assess the temporal variation of herbivore amphipods, of the Ampithoidae family, and of the brown seaweed Sargassum filipendula and its epiphytes. In addition, we explore the effects of the consumption of algae with different characteristics (Sargassum filipendula and two epiphytes, Dictyota filosa and Sunampithoe pelagica) on the fitness of two ampithoids, Cymadusa filosa and Sunampithoe pelagica, as well as on their feeding preference and rate. The composition of Ampithoidae species displayed temporal variation and was influenced by the Sargassum biomass and the intensity of epiphytism. Sunampithoe pelagica revealed itself as the most abundant species of Ampithoidae, and was strongly associated to the Sargassum biomass. The C. filosa, Ampithoe marcuzzi and A. ramondi species were less abundant, and they accompanied the variation of the epiphyte biomass. In the fitness experiments, young S. pelagica being fed Sargassum, as compared to the groups being fed Hypnea and Dictyota, displayed larger survival rates. This suggests that this species has a restricted diet. Regarding C. filosa, the survival rate was similar for the young specimens subjected to three diets, but those fed Sargassum showed greater growth and higher reproductive success. In a multiple choice experiments, C. filosa and S. pelagica adults were shown to prefer consuming Sargassum. When they were not offered a choice, C. filosa adults consumed the three algae at the same rate. In contradistinction to this, in the feeding rate experiment S. pelagica adults consumed Sargassum the most. In spite of the two amphipod species displaying greater preference and success rates when consuming Sargassum, they reacted differently when other algae was offered them, which might explain the observed differences regarding their occurrence patterns in the field. Therefore, as an important factor of herbivore-macroalgae interaction, feeding can influence the responses of herbivorous amphipods to changes in macroalgae biomass. Furthermore, our results stress the importance of considering the specificities of each herbivore in order to understand the impact of these animals on the community of algae
Mestrado
Ecologia
Mestre em Ecologia

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Vendemiatti, Eloisa. "Compreendendo a via de desenvolvimento de tricoma glandular em tomateiro (Solanum lycopersicum) utilizando mutantes e variações genéticas naturais." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11144/tde-28092015-175150/.

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Os tricomas são estruturas de origem epidérmicas que podem ser classificados em dois tipos: glandulares e não glandulares (tectores) e estão relacionados, principalmente, com estratégias de defesas de plantas. Pouco se conhece sobre a via de desenvolvimento dos tricomas glandulares, já que a maior parte dos estudos é em Arabidopsis thaliana, modelo no qual os tricomas glandulares são ausentes. O gênero Solanum possui uma grande diversidade de tricomas, em especial glandulares (tipos I, IV, VI e VII). O estudo de tais estruturas vem ganhando cada vez mais destaque, já que são fontes de diversos metabólitos secundários de importância econômica e ecológica. Espécies selvagens são consideradas recursos genéticos para o tomateiro (S. lycopersicum), tais como S. galapagense, a qual possui variações genéticas naturais que lhe confere maior resistência ao ataque de herbívoros. Entre essas variações está a presença de tricomas glandulares do tipo IV, uma fonte do aleloquimico acilaçúcar. A ausência de tricomas glandulares do tipo IV é considerada uma das causas da suscetibilidade do tomateiro cultivado a insetos. No presente trabalho, foi demonstrado que o tomateiro cultivado na verdade forma tricomas do tipo IV, mas estas estruturas estão presentes somente até o primeiro par de folhas, além dos cotilédones. Desse modo, a presença de tricomas tipo IV em espécies selvagens seria considerada uma neotenia, ou seja, a manutenção de estruturas juvenis na fase adulta. Além de se determinar que mutantes de tomateiro afetando a juvenilidade (e.g. Mouse ears e fasciated) apresentam tricomas tipo IV na fase adulta, a formação dessas estruturas correlacionou se com a expressão de miR156, sendo também presentes em grandes quantidades em uma linhagem transgênica superexpressando esse micro RNA relacionado à juvenilidade. Quanto à base genética da presença de tricomas tipo IV nas espécies selvagens, no presente trabalho foi criada uma linhagem quase isogênica ao modelo genética Micro-Tom (MT) contendo a variação genética natural por nós denominada Galapagos enhanced trichomes (Get). Tal variação é derivada de S. galapagense e condiciona a presença de tricomas tipo IV em folhas adultas, quando introgredida em tomateiro cultivado (cv. Micro-Tom). O mapeamento preliminar de Get no cromossomo 2 de tomateiro também foi realizado através do mapa de \"single nucleotide polymorphism\" (SNPs) entre MT e a linhagem MT-Get. A eventual clonagem de GET irá contribuir não somente para se desvendar a base genética da formação de tricomas glandulares, como também contribuir para se criar variedades resistentes a insetos, reduzindo o uso de agrotóxicos.
Trichomes are epidermal structures that can be classified into two types: glandular or non-glandular, and they are mainly related to plant defense strategies. Little is known about the glandular trichome development pathway, since most of the studies are in Arabidopsis thaliana, a model in which this kind of trichome is absent. The Solanum genus has a wide variety of trichomes, especially glandular ones (Types I, IV, VI and VII). The study of these structures are gaining more prominence, since they are sources of several secondary metabolites of economic and ecological importance. Wild species are considered genetic resources for tomato (S. lycopersicum), such as S. galapagense which has natural genetic variations that gives resistance to herbivores attack. Among these variations is the presence of type IV glandular trichomes, a source of the acyl sugar allelochemical. The absence of type IV glandular trichomes is considered to be one of the causes of tomato susceptibility to insects. In this study, it was determined that tomato actually has type IV trichomes, but these structures are present only in the cotyledons and the first pair of leaves. Thus, the presence of type IV trichomes in wild species would be considered a neotenic feature, i.e. the maintenance of juvenile structures in adulthood. In addition, it was determined that tomato mutants affecting youthfulness (e.g. Mouse ears and fasciated) have type IV trichomes in adulthood. Moreover, the presence of these structures was correlated with the expression of miR156, besides the increased formation of type IV trichomes in a transgenic line overexpressing this micro RNA related to youthfulness. On the genetic basis of type IV trichomes presence in wild species, in this work it was created a near isogenic line (NIL) containing the natural genetic variation here named Galapagos enhanced trichomes (Get). This variation is derived from S. galapagense and harbors type IV trichomes in adult leaves, when introgressed in cultivated tomato (cv. Micro-Tom). The preliminary genetic map of Get in the tomato chromosome 2 was conducted through the analysis of \"single nucleotide polymorphism\" (SNPs) between MT and MT-Get. The eventual cloning of GET will contribute not only to unravel the genetic basis of glandular trichomes formation, but will also contribute to create varieties resistant to insects, reducing the pesticides use.

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Pizzi, Marcello Bontempi [UNESP]. "Perdas de produtividade de 12 clones de eucalipto submetidos a desfolhas artificiais sucessivas." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144286.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A produtividade de plantios de eucalipto no Brasil foi triplicada nas últimas quatro décadas graças, principalmente, à pesquisa intensiva, investimentos em tecnologia silvicultural, clonagem e melhoramento genético. Atualmente, existem diversas pesquisas relacionadas ao gênero Eucalyptus, mas são poucas as que abordam o tema estresse biótico por ser uma avaliação complexa e de difícil planejamento e execução. Em Piracicaba, em um sítio experimental com alta sanidade e sobrevivência, foram induzidas uma, duas e três desfolhas sucessivas, retirando-se manualmente todas as folhas da copa das árvores de 12 clones de eucalipto de extrema relevância à silvicultura brasileira. As desfolhas ocorreram aproximadamente aos 15, 19 e 23 meses de idade das árvores, e a avaliação final de perda de produtividade ocorreu aos 27 meses. O crescimento das árvores foi monitorado semanalmente, sendo possível ver o efeito das desfolhas ao longo do período. Os clones de eucalipto escolhidos para este estudo, apesar de pertencerem ao mesmo gênero, mostraram resultados bastante diferentes. O impacto das desfolhas no crescimento das árvores foi imediato e prolongado, com o crescimento próximo à zero por 50 a 120 dias após a desfolha. As desfolhas causaram redução de crescimento em DAP (Diâmetro à Altura do Peito), altura total, volume e biomassa de madeira. As árvores não desfolhadas acabaram dominando as desfolhadas. Isso causou o estiolamento das árvores desfolhadas e a redução da homogeneidade das parcelas. Aos 27 meses, as árvores que sofreram uma desfolha apresentaram biomassa de madeira 48% inferior ao das árvores que não sofreram desfolhas (variando entre 24 e 57% para clones). Duas desfolhas sucessivas causaram redução média de 59% de biomassa (variando entre 49 e 72%) e três desfolhas sucessivas causaram perdas médias de 68% (variando entre 57 e 80%).
The Brazilian Eucalyptus productivity has tripled in the last four decades, mainly because of intensive research, development of forestry and genetics. Nowadays, there are several studies related to the Eucalyptus genus, but only a few address biotic stress, as the subject is of complex evaluation, difficult planning and execution. In Piracicaba, in an experimental site with high health and survival rate, one, two and three successive defoliations were induced, manually removing all the canopy leaves of 12 extremely relevant clones to Brazilian forestry. The defoliations occurred in approximately 15, 19 and 23 months after planting and the final evaluation of productivity occurred at 27 months. Tree growth was weekly monitored, and the effect of defoliation over time was visible. The eucalypts clones chosen for this study, despite belonging to the same genus, showed quite different results. The impact of canopy defoliation on tree growth was immediate and prolonged, with growth close to zero for 50 to 120 days following defoliation. Defoliation caused growth reduction in DBH (Diameter at Breast Height), total height, volume and wood biomass. Defoliated trees were etiolated as the non-defoliated were the dominant trees in the plot. Defoliation reduced plot homogeneity. One year after the first defoliation, the 27-month-old trees that have undergone one defoliation showed 48% lower wood biomass, in comparison with non-defoliated trees (ranging from 24 to 57% by clones). Two successive defoliations caused an average reduction of 59% of biomass (ranging from 49 to 72%) and three successive defoliations caused 68% of losses (ranging from 57 to 80%).

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Valdes, correcher Elena. "Drivers of insect herbivory in Pedunculate oak (Quercus robur) from tree to biogeographical scale." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0034.

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L'herbivorie par les insectes est un processus écologique important qui affecte la dynamique des populations de plantes, les communautés et les écosystèmes. La distribution et l'abondance des insectes herbivores et l'activité qui en résulte sont façonnées par une multitude de facteurs, intrinsèques ou extrinsèques à la plante hôte, qui agissent à différentes échelles spatiales et souvent de concert. Une classification largement utilisée fait la distinction entre les forces ascendantes, telles que l'activité des herbivores est influencée par la distribution et la qualité des ressources (incluant les défenses), et les forces descendantes, telles que l'activité des herbivores est limitée par le contrôle exercé par les ennemis des herbivores (prédateurs, parasitoïdes). Les forces ascendantes et descendantes sont toutes deux impliquées dans les cascades trophiques qui accompagnent inévitablement les interactions plantes-herbivores dans les populations naturelles de plantes, mais leur importance relative peut varier considérablement selon le contexte particulier local, et les mécanismes biologiques sous-jacents restent mal compris.J'ai étudié les facteurs écologiques qui façonnent les relations entre le chêne pédonculé (Quercus robur) et ses insectes herbivores à différentes échelles spatiales. En particulier, j'ai examiné les effets du contexte du paysage, de l’apparentement entre les arbres et du climat sur l'activité des herbivores. Un des principaux objectifs de ma thèse était d'évaluer l'importance relative des forces ascendantes et descendantes dans la structuration des relations chêne-herbivores.La thèse est structurée en trois chapitres principaux correspondant à des manuscrits indépendants qui publiés (chapitre 1), en cours de révision (chapitre 2), ou en préparation (chapitre 3) au moment de la soumission du document de thèse. Dans le chapitre 1, j'ai étudié la relation entre l'herbivorie et la communauté et l'activité des oiseaux insectivores dans les chênaies qui diffèrent en taille et en connectivité. J'ai constaté que l'herbivorie, la prédation des oiseaux et les communautés d'oiseaux étaient influencées par les caractéristiques du paysage, mais que ni la prédation sur les herbivores ni les communautés d'oiseaux n'avaient d'effet significatif sur l'herbivorie. Dans le chapitre 2, j'ai étudié la relation entre le génotype du chêne, les défenses chimiques des feuilles et l'herbivorie dans les mêmes peuplements. J'ai constaté que l'herbivorie des insectes et les défenses chimiques étaient non seulement influencées par les caractéristiques du paysage, mais aussi par le génotype de l'arbre, et que l'herbivorie des insectes diminuait avec la concentration des défenses foliaires. Enfin, au chapitre 3, j'ai étudié l'effet de la variabilité climatique à grande échelle sur les interactions entre les plantes, l'herbivorie et la prédation des oiseaux dans les chênes selon un gradient latitudinal. J'ai découvert que les facteurs climatiques influençaient l'herbivorie des insectes ainsi que les caractéristiques nutritionnelles des feuilles, alors qu'ils n'influençaient pas les défenses foliaires et la prédation des oiseaux. De plus, l'herbivorie des insectes n'était influencée que par des forces ascendantes dont l’importance variait selon les guildes d’insectes.Dans l'ensemble, ces résultats aident à améliorer notre compréhension des différentes forces écologiques qui façonnent l'herbivorie par les insectes et de leur variabilité dans les populations naturelles d'arbres. Les études futures sur les interactions plantes-herbivores-prédateurs devraient tenir compte du fait que celles-ci sont influencées simultanément par le génotype de la plante hôte, les caractéristiques du paysage et le climat. Enfin, la thèse illustre également la valeur des approches de science citoyenne qui peuvent combiner la recherche scientifique avec une éducation scientifique et à l’environnement bien nécessaires
Insect herbivory is an important ecological process that affects plant populations, communities and ecosystems. The distribution and abundance of insect herbivores and their resulting activity are shaped by a multitude of drivers, intrinsic or extrinsic to the host plant, that act at different spatial scales and often in concert. A widely used classification distinguishes between bottom-up forces where herbivore activity is influenced by the distribution and dynamics of the resource stock (including the defenses), and top-down forces where herbivore activity is constrained by drivers of mortality (e.g. predators, pests). Both bottom-up and top-down forces are involved in the trophic cascades that inevitably accompany plant-herbivore interactions in natural plant populations, yet their relative importance can vary greatly depending on the particular study context, and the underlying biological mechanisms remain poorly understood.I investigated the ecological drivers shaping the relationships between Pedunculate oak (Quercus robur) and its insect herbivores across different spatial scales. In particular, I examined the effects of the ecological neighbourhood, the landscape context, tree genetic relatedness and climate on herbivore activity. A major aim of my thesis was to evaluate the relative importance of bottom-up and top-down forces in shaping oak-herbivore relationships.The thesis is structured in three main chapters corresponding to independent manuscripts that are either published (chapter 1), under review (chapter 2) or under preparation (chapter 3) at the moment of submitting the thesis document. In chapter 1 I investigated the relationship between herbivory and the community and activity of insectivorous birds in oak stands that differed in size and connectivity. I found that herbivory, bird predation and bird communities were influenced by landscape characteristics, but neither predation on herbivores nor bird communities had a significant effect on herbivory. In chapter 2 I investigated the relationship between oak genotype, leaf defences and herbivory in the same stands. I found that insect herbivory and leaf defences were not only influenced by landscape characteristics but also by the genotype of the tree, and that insect herbivory decreased with increasing concentration of leaf defences. Finally, in chapter 3 I investigated the effect of large-scale climate variability on the interactions between plants, herbivory and bird predation in oak trees along a latitudinal gradient. I found that climatic factors influenced insect herbivory as well as leaf nutritional traits, while they did not influence leaf defences and bird predation. Furthermore, insect herbivory was only influenced by bottom-up forces (e.g. leaf nutritional traits and leaf defences) and these effects on herbivory varied among herbivore feeding guilds, while neither other traits nor top-down forces affected insect herbivory.Overall, these results help improve our understanding of the different ecological forces shaping insect herbivory and their bottom-up and top-down drivers in natural tree populations. Future studies of plants-herbivores-predator interactions should take into account that these are simultaneously influenced by host plant genotype, landscape characteristics and climate. Finally, the thesis also illustrates the value of citizen science approaches that can combine scientific research with much-needed environmental education

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Lundgren, Andreas. "Relation between herbivore abundance, herbivore diversity and vegetation diversity." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-150095.

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Legendre, Héloïse. "Approche agro-écologique de la gestion du parasitisme en élevage : application en système cunicole biologique." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0101.

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L’étude des interactions entre système fourrager, santé et croissance des lapins contribuera à proposer de nouvelles pratiques pour des systèmes d’élevage cunicole alternatifs, tels que ceux en agriculture biologique (AB) incluant une gestion intégrée de la santé. Mais cette stratégie est limitée par le manque de références sur la cuniculture AB, i) sur l'alimentation au pâturage (ingestion de fourrages verts, qualités nutritionnelles pour les lapins, etc) ; et ii) sur les risques sanitaires notamment le parasitisme, identifié comme un frein important au développement de la cuniculture AB. L’emploi de plantes riches en tannins condensés (TCs) comme le sainfoin, permettrait de diminuer l’utilisation d’antiparasitaires comme cela a été montré chez les petits ruminants, tant pour la gestion des nématodes que celle des coccidies. Mais le potentiel d’activité des TCs chez le lapin, tout comme le niveau d’ingestion et les performances de croissance, restent à explorer, et pourra servir la cuniculture AB et conventionnelle. Ce travail de thèse a pour objectif i) d’étudier l’intérêt du sainfoin comme ressource pour l’alimentation du lapin, et pour ses propriétés antiparasitaires, ii) définir le niveau d’ingestion au pâturage des lapins et les conséquences sur la production et iii) d’évaluer, le risque parasitaire au pâturage pour des lapins en production. Nous avons montré qu’un aliment enrichi en sainfoin distribué à partir du sevrage, avec une teneur en tannins de 1,8% d’équivalent d’acide tannique, n’a pas réduit l’installation de L3s de Trichostrongylus colubriformis, ni la fertilité des vers adultes, mais a réduit le potentiel d’éclosion des oeufs (-27 points), contribuant à réduire l’infestation de l’environnement. Un aliment enrichi en sainfoin contenant 1,2% d’équivalent d’acide tannique, distribué aux mères et aux lapins en croissance a eu un effet coccidiostatique : l’excrétion oocystale fécale de lapins nourris avec un aliment enrichi en sainfoin a été réduite de 60% par rapport à ceux ayant reçus l’aliment témoin. Si la réduction de l’excrétion oocystale de l’espèce Eimeria magna n’a pas pu être démontrée, en revanche, la réduction d’oocystes toutes espèces confondues dans l’environnement pourrait contribuer à diminuer le risque de coccidiose en élevage. Comparé à la luzerne, le sainfoin, plus riche en lignines, a une forte concentration en énergie (11,2 MJ/kg) et en protéines digestibles (110 g/kg). Au pâturage, lorsque la quantité d’herbe offerte dépasse 85 g MS/kg0,75, il semble que l’ingestion d’herbe soit régulée d’une part lorsque la teneur en énergie digestible de l’herbe dépasse 9 MJ/kg (régulation chémostatique), ou d’autre part si la teneur en lignocellulose (ADF) dépasse 350 g d’ADF/kg (régulation physique : encombrement digestif). Mais la quantité d'herbe disponible dépasse rarement 85 g MS/kg0,75. C’est-à-dire que dans la majorité des cas, une surface pâturable de 0,4 m² (minimum réglementaire) n’a pas permis de combler la capacité d’ingestion et les besoins énergétiques de lapin en croissance. De plus, si l’offre d’herbe est limitante, le lapin ne peut pas exprimer une préférence alimentaire vers des plantes plus jeunes et riches en protéines. La limitation de l’ingestion de protéines a aussi pour conséquence de réduire les potentialités de croissance des lapins et d’allonger la période d’engraissement. Au cours de trois saisons successives de pâturage (université de Perpignan), la pression parasitaire (nématodes et coccidies) a augmenté, avec des infestations par Trichostrongylus sp. et de Graphidium strigosum. Si le délai d'attente entre deux pâturages n’a pas eu d’effet visible sur l’infestation par des nématodes, cela influerait le niveau d’infection par les coccidies. Nos travaux établissent l’intérêt de l’incorporation du sainfoin dans l’alimentation du lapin et ouvrent des perspectives pour établir des pratiques innovantes et bénéfiques à la production cunicole biologique et conventionnelle
The study of the interactions between grazing systems, health and growth in organic rabbit farming (ORF) will contribute to propose new practices including integrated management of health. However, this strategy is limited by the lack of references on ORF and in particular on rabbit intake of green fodder when grazing, nutritional qualities of forages for rabbits, the supply of grass in relation with animal’s density (stocking rate), the related parasitic challenge, etc. The acquisition of such references is a key issue for the development of ORF. The use of plants rich in condensed tannins (CTs), such as sainfoin, could reduce the use of antiparasitic agents, as shown in small ruminants, both for the management of nematodes and for coccidia. However, the potential for CTs containing resources in rabbits, as well as the intake levels and the effects on growth performances, remain to be explored in both OF and conventional rabbit breeding. The aim of this thesis was (i) to investigate the interest of sainfoin as a resource for rabbit feeding and its antiparasitic properties, (ii) to define the intake level in grazing rabbit and the consequences on production and (iii) to evaluate the parasitic risk associated with pasture for rabbits’ production. We have shown that a sainfoin-enriched diet distributed from weaning, with a feed containing 1.8% of tannic acid equivalent, did not reduce neither the establishment of Trichostrongylus colubriformis L3s, nor the fertility of adult worms. In contrast, the development of nematode’s egg to infective larvae was compromised and may reduce the risk of environmental contamination. Besides, a sainfoin-enriched diet containing 1.2% tannic acid equivalent, distributed to does and growing rabbits, had a coccidiostatic effect. With an overall fecal oocyst excretion in rabbits fed with sainfoin reduced by 60% compared to control diet. Although, the pathogenic species Eimeria magna was not concerned by these decrease, such a general reduction in oocyst excretion in the environment could help to reduce on long term the risk of coccidiosis in the rearing units. Sainfoin could constitute a real alternative to dehydrated alfalfa, since it has high digestible energy (DE, 11.12 MJ DE/kg), and protein (110 g/kg), and provide a high supply of lignins. At grazing, when the herbage allowance exceeded 85 g DM/kg0,75, it appeared that the herbage intake was limited by an increase in the DE content when it exceeds 9 MJ / kg, or else by a lignocellulose content higher than 350 g of ADF/kg. However, herbage allowance, rarely exceeds 85 g DM/kg0,75. In other words, in the majority of cases access to a 0.4 m² grazing area did not allow sufficient supply to reach the intake capacity and energy requirements of the rabbits. In addition, rabbits with limited supply cannot express their dietary preference to young and high protein plants. Limiting the intake of proteins also reduced the growth potential of rabbits and extended the fattening period. During the first three grazing seasons (University of Perpignan), the parasitic pressure (nematodes and coccidia) increased, particularly with cases of Trichostrongylus sp. and Graphidium strigosum. While rotation rhythms had no visible effects on nematode infestation, it had an influence on coccidian infection. This work enabled us to establish the advantage of sainfoin enriched diet for the rabbit. It gives prospects to further research projects regarding the establishment of beneficial and innovative practices for organic and conventional rabbit breeding

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Jorge, Leonardo Ré 1985. "Reformulation of the concept of trophic specialization and its application to species and communities." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315721.

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Orientador: Thomas Michael Lewinsohn
Texto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Nesta tese propomos um desenvolvimento do conceito de especialização no uso de recursos, de forma a incluir aspectos pouco considerados, principalmente no contexto de interações: afinidades entre os tipos de recursos, sua disponibilidade e padrões de coocorrência. Por meio da incorporação de avanços recentes em estudos ecofilogenéticos e em modelos nulos, propomos novas métricas para a especialização de espécies e comunidades, e aplicamos esses avanços para responder a questões particulares. No primeiro capítulo, o arcabouço conceitual é apresentado de forma mais geral, e uma métrica para a especialização de espécies é proposta e exemplificada. O segundo capítulo, de natureza metodológica, estende essa métrica para comunidades e propõe uma partição da variação em especialização entre espécies e entre locais de forma hierarquizada. O terceiro capítulo investiga a capacidade destas ferramentas de evidenciar relações entre a especialização e a distribuição geográfica de espécies de insetos endófagos de capítulos de Asteraceae no Brasil. Por fim, o quarto capítulo utiliza o mesmo conjunto de dados para investigar o papel da diversidade filogenética de recursos na determinação da riqueza de insetos que os utilizam
Abstract: In this thesis we propose a development of the resource specialization concept to include aspects usually not taken into account, especially for trophic interactions: affinities among resource types, their availabilities and cooccurrence patterns with consumers. By incorporating recent advances in ecophylogenetics and null modelling, we propose new metrics for the specialization of species and communities and apply these advances to address particular questions. In the first chapter the general conceptual framework is presented and a metric for the specialization of species is proposed and exemplified. The second chapter, mostly methodological, expands this metric for communities and proposes a hierarchical partitioning of the variation in specialization among species and locations. The third chapter tests this toolset in showing the relationship between specialization and geographic distribution ranges of endophagous insects feeding in Asteraceae flowerheads in Brazil. Finally, the fourth chapter uses the same dataset to investigate the role of phylogenetic diversity of resources in determining the richness of insect herbivores using them
Doutorado
Ecologia
Doutor em Ecologia

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Gard, Benjamin. "Processus écologiques et évolutifs influençant la colonisation de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia L.) en France." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00985748.

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La compréhension des mécanismes déterminant le succès des espèces invasives est une étape essentielle dans la gestion des invasions biologiques actuelles et la prédiction des futurs risques d'invasion. En adoptant un cadre d'étude conceptuel intégrant les processus écologiques et évolutifs, l'objectif de ce travail était d'analyser les déterminants de la colonisation de l'ambroisie à feuilles d'armoise en France. Tout d'abord, l'étude des interactions biotiques et abiotiques a permis de montrer la capacité de tolérance de l'ambroisie à l'herbivorie et au stress hydrique. L'ambroisie est capable de tolérer la défoliation grâce à une croissance compensatoire efficace, sans que sa reproduction en soit affectée. Cette forte tolérance à l'herbivorie est maintenue chez les populations introduites, malgré la faible pression des ennemis naturels dans la zone d'introduction. En condition de stress hydrique, l'ambroisie produit une biomasse racinaire supérieure aux espèces présentes dans les communautés qu'elle envahit. De plus, les différences dans les valeurs moyennes pour les traits mesurés suggèrent une occupation différente par l'ambroisie des niches écologiques disponibles. La comparaison en jardins communs de populations de l'aire d'origine avec des populations de l'aire d'introduction isolées et issues du foyer central d'invasion a montré que l'adaptation de l'ambroisie à son environnement reposait principalement sur la plasticité phénotypique plutôt que sur la différenciation des traits. Les études de génétiques quantitatives ont mis en évidence un potentiel évolutif élevé pour les traits liés à la germination. Les traits liés à la morphologie, à la phénologie et à la physiologie de la plante montrent une variance additive et une héritabilité plus faibles et donc un potentiel évolutif moindre. En revanche, la variation dans les normes de réaction indique un potentiel évolutif important de la plasticité phénotypique. La tolérance au stress hydrique et à l'herbivorie sont des facteurs qui potentiellement augmentent la capacité de l'ambroisie à coloniser une large gamme d'habitat. De plus, la plasticité phénotypique et le potentiel évolutif important peuvent favoriser une augmentation ou un déplacement de la niche écologique de l'espèce et ainsi favoriser l'expansion de son aire de répartition

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Vieira, Christophe. "Lobophora : biotic interactions and diversification." Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066195.

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L'algue brune Lobophora représente une composante benthique importante au sein des récifs coralliens tropicaux, et a à attirer dès le début des années 80 l'attention des écologistes marins en proliférant de façon remarquable au détriment des coraux. Les écologistes marins ne s’accordent toujours pas pour conclure si le changement de communauté au profit des macroalgues représente une conséquence ou une cause de la dégradation des coraux. Alors que Lobophora a fait l'objet d'observations contradictoires en termes de susceptibilité à l’herbivorie et des effets sur les coraux, les preuves suggèrent que sa prolifération dans les récifs coralliens est opportuniste et symptomatique de la dégradation des récifs. Taxonomiquement, Lobophora ne représentait que 11 espèces décrites au début de cette étude, et pratiquement toutes les espèces de Lobophora rapportées dans le monde avaient été assignées à L. variegata, décrite dans les Caraïbes. Cette étude vise à apporter un nouvel éclairage taxonomique et écologique sur ce taxon algal sujet de controverses écologiques. En utilisant une approche taxonomique basée sur l'ADN nous avons réévalué la diversité des espèces de ce genre en Nouvelle-Calédonie et au niveau mondial. Les résultats dévoilent une remarquable diversité, multipliant par 10 le nombre d’espèces jusque là reconnues. Nous avons testé si les différentes espèces de Lobophora étaient chimiquement différentes et si elles variaient (1) en toxicité envers différents coraux, et (2) en susceptibilité aux herbivores. Nous avons montré que le genre Lobophora était intrinsèquement capable de blanchir certains coraux, et nous avons isolé trois nouveaux alcools polyinsaturés C21 nommés lobophorenols A-C avec des propriétés de blanchissement. Néanmoins, les observations in situ en Nouvelle-Calédonie indiquent que, bien qu’elles soient potentiellement armées au plan chimique, les espèces de Lobophora n’induisent pas ou rarement le blanchissement de leurs hôtes coralliens, soulevant ainsi la question de l'emplacement de ces composants bioactifs dans l’algue et des facteurs environnementaux permettant leur libération supposée. Nous avons également montré que les herbivores consomment indistinctement les espèces de Lobophora. D’après ces résultats nous pouvons conclure que : (1) au sein de récifs en bonne santé, les coraux et les Lobophora maintiennent un statu quo résultant probablement d’une médiation chimique ; (2) la défense chimique ne dissuade apparemment pas le broutage des Lobophora par les principaux herbivores ; (3) il est probable que Lobophora échappe au broutage en se développant par exemple entre les branches des coraux. Le genre Lobophora représente un excellent modèle pour étudier le rôle de la spéciation écologique des algues au sein des récifs coralliens. Aussi, les études futures devront étudier le rôle des métabolites secondaires des Lobophora et enquêter sur les facteurs écologiques responsables de la diversification impressionnante de cette algue
The brown alga Lobophora represents a notable benthic component in tropical coral reefs, and began drawing the attention of marine ecologists by achieving impressive blooms at the expense of corals since the early 80s. Marine ecologists are still debating whether or not macroalgal dominance represents a consequence or cause of coral degradation. While Lobophora has been the object of contradictory observations in terms of susceptibility to herbivory and effects on corals, evidence tends to suggest that episodes of reef take-over are opportunistic and symptomatic of reef degradation. From a taxonomic point of view, only 11 species of Lobophora were recognized at the beginning of this study, and virtually all species of Lobophora reported around the world had been assigned to L. variegata, originally described from the Caribbean. This study intends to shed new taxonomical and ecological insights on this algal taxon. Using a DNA-based taxonomical approach we reassessed the species diversity of this genus at a local scale in New Caledonia and subsequently on a global level. Results disclosed a remarkable global diversity, increasing our taxonomic knowledge of this genus by no less than 10 folds. From an ecological perspective, we tested if different species of Lobophora were differentially (1) capable of chemically damaging scleractinian corals, and (2) susceptible to herbivory. We showed that the genus Lobophora was inherently capable of bleaching certain coral species, and we isolated three new C21 polyunsaturated alcohols named lobophorenols A-C with bleaching properties. Nevertheless, in situ observations in New Caledonia indicated that although potentially chemically armed, Lobophora species did not or rarely bleached their coral hosts, thereby raising the issue of the location of these bioactive components and the environmental factors enabling their putative release by the alga. We also showed that herbivores indiscriminately consumed Lobophora species. From the results of allelopathic bioassays and grazing experiments we conclude that: (1) corals and Lobophora maintain a chemical-mediated status quo on healthy reefs; (2) chemical defense apparently does not deter grazing of Lobophora by prominent herbivores; (3) it is more likely that Lobophora avoids being grazed by escape strategies such as growing under the coral canopy. The genus Lobophora represents an excellent model to study the role of ecological speciation in macroalgae within coral reefs. Therefore, future studies should be targeted at investigating the role of Lobophora secondary metabolites and exploring the ecological factors responsible for the impressive diversification of this alga

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Silva, Walciria Alves da. "Danos foliares por herbivoria em florestas de mangue em três estuários do estado da Paraíba." Universidade Federal da Paraíba, 2014. http://tede.biblioteca.ufpb.br:8080/handle/tede/7618.

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The frequency of damage and herbivory rate on leaves of Avicennia schaueriana Stapf & Leechm ex Moldenke, Laguncularia racemosa (L.) Gaertn.f. and Rhizophora mangle L. were evaluated in three mangroves forest (Sites 1, 2 and 3) adjacent to hypersaline areas in Paraíba, State of Brazil, in order to verify interspecific and intraspecific variation. Nine types of damage were identified: hole, fungus, gall, undefined, damage on the leaf margin, mine, necrosis, egg and rasping. Laguncularia racemosa presented the highest frequency of damage and higher average rate of herbivory (3.17 to 7.07 %) compared to Rhizophora mangle (0.77 to 1.76%) and Avicennia schaueriana (0.36 to 0.91%). There were significant intraspecific differences in leaf damage and herbivory rates among study sites, with no specific pattern. Laguncularia racemosa presented the hardest leaves (weight/area) in relation to other species. In general, the correlation between the hardness of the leaves (weight/area) and grazing rates were low or positive, suggesting that other factors, such as chemical, soil conditions (eg. interstitial salinity) and herbivores involved, can affect on herbivory process. The grazing values obtained in this study are considered low compared to other mangrove.
A frequência de danos e a taxa de herbivoria em folhas maduras de Avicennia schaueriana Stapf & Leechm ex Moldenke, Laguncularia racemosa (L.) Gaertn.f. e Rhizophora mangle L. foram avaliadas em três florestas de mangues (Sítios 1, 2 e 3) adjacentes a planícies hipersalinas no Estado da Paraíba, Brasil, para verificar se existe variação interespecífica e intraespecífica. Nove tipos de danos foram identificados: buraco, fungo, galha, indefinido, margem, mina, necrose, ovo e raspagem, sendo Laguncularia racemosa a espécie que apresentou maior frequência de danos e maior taxa de herbivoria média (3,17 a 7,07%) comparada com Rhizophora mangle (0,77 a 1,76%) e Avicennia schaueriana (0,36 a 0,91%). Houve diferenças intraespecíficas significativas para danos foliares e taxas de herbivoria entre os sítios de estudo, sem padrão específico. Laguncularia racemosa apresentou maior razão peso úmido/área das folhas (peso/área) em relação às demais espécies. Em geral, as correlações entre a razão peso úmido/área das folhas (peso/área) e as taxas de herbivoria foram baixas ou positivas, sugerindo que outros fatores, tais como características químicas, condições edáficas (ex. salinidade intersticial), bem como os herbívoros envolvidos, podem exercer maior influência no processo de herbivoria. Os valores de herbivoria obtidos neste estudo são considerados baixos em relação a outros manguezais.

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Giffard, Brice. "Influence des interactions biotiques complexes sur la régénération des essences forestières feuillues." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14319/document.

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Les herbivores consomment les tissus végétaux et affectent la survie et la croissance des végétaux. Les ennemis naturels des herbivores peuvent réguler leurs populations et indirectement diminuer les dommages sur la végétation. Les relations entre plantes, herbivores et prédateurs sont liées aux caractéristiques intrinsèques des espèces végétales mais aussi influencées par la communauté végétale environnante. L'hypothèse de résistance par association stipule qu'une communauté végétale diversifiée entraîne une diminution des dégâts sur une plante cible par dilution, répulsion des herbivores et/ou favorisation des ennemis naturels. Inversement, les herbivores peuvent se concentrer sur la plante-cible dans une communauté végétale diversifiée (susceptibilité par association). L'objectif de cette thèse est d'évaluer 1) l'influence de la composition de la communauté végétale sur les herbivores et leurs dommages sur une plante-cible, 2) l'impact de la régulation des herbivores par les prédateurs et 3) les interactions entre herbivores, communauté végétale et prédateurs, et les conséquences pour les intensités d'herbivorie sur la plante-cible. Nous nous sommes focalisés sur les dommages causés par les insectes herbivores sur des plantules d'essences forestières feuillues (Betula pendula, Quercus robur et Q. ilex). La variété importante de communautés végétales, au niveau inter (essences dominantes) et intraparcellaire (présence, structure et composition), nous a permis de tester les effets du voisinage végétal sur les insectes herbivores et leurs dommages sur les plantules cibles. Les oiseaux insectivores sont les principaux prédateurs d'insectes et nous avons cherché à estimer les effets de leur exclusion sur les insectes et les conséquences pour les plantules, et ceci le long des gradients de composition du voisinage végétal. Enfin, le degré de spécialisation (spécialiste/généraliste) et le mode de vie (exo/endophyte) ont été caractérisés car ils conditionnent les réponses des insectes herbivores à la végétation voisine ainsi que la prédation avienne. Le voisinage végétal des plantules-cibles modifie la charge en herbivores et les dommages engendrés. Ces réponses sont liées à la spécialisation de l'insecte herbivore : la colonisation des plantules par les espèces spécialistes (mineuses de feuilles) est négativement affectée par la structure de la végétation locale (présence, recouvrement arbustif). Les dommages d'insectes généralistes augmentent avec la richesse spécifique des peuplements et dans les parcelles dominées par des espèces conspécifiques. Les abondances des insectes externes et leurs dommages sont régulés par les oiseaux insectivores mais cet effet indirect dépend de l'espèce de plantule-cible et de la composition de la communauté végétale. Les effets de cascade trophique sont les plus intenses dans les parcelles de pin maritime où les plantules constituent une ressource nouvelle pour les niveaux trophiques supérieurs. Plus localement, le voisinage végétal modifie la sensibilité des arthropodes à la prédation: les oiseaux insectivores bénéficient aux plantules lorsque les proies sont plus accessibles (végétation environnante supprimée).Pour conclure, une des principales richesses de ces résultats vient de la mise en évidence d'interactions très fortes existant entre les effets des oiseaux insectivores et la végétation environnante. Les effets indirects des prédateurs et directs de la végétation environnante sont très liés au degré de spécialisation des insectes phytophages et à leur mode de vie
Herbivory is thought to depend on intrinsic plant resistance traits and negatively affect survival and growth of plants. Predators can depress herbivore populations and thereby indirectly limit the consumption of primary producers. The surrounding vegetation is also expected to modify the interactions between a focal plant, its herbivores and their natural enemies. The surrounding vegetation may disrupt the colonisation and the consumption of a focal plant by insect herbivores, providing associational resistance. Increasing diversity of neighbouring vegetation can decrease resource availability or enhance herbivores control by predators. By contrast, associational susceptibility may occur with higher levels of herbivory in a focal plant in more diverse plant communities. We tested 1) the effect of the neighbouring vegetation on the levels of herbivory on seedlings, 2) the indirect impact of predators on herbivores and subsequent herbivory, and 3) the interactions between surrounding vegetation, focal plants, herbivores and predators. We examined the damage caused by insect herbivores on three native broadleaved species. We then compared the importance of taxonomic similarity between seedlings and canopy tree species and the structure and composition of surrounding vegetation at both large- and small-scales. Birds are vertebrate predators likely to limit damage to plants and facilitate plant growth by consuming herbivorous insects. We estimated their effects by excluding them from focal plants, and compared their interactive effects with vegetation diversity or removal. The effects of surrounding vegetation and avian predation were also disentangled on concealed- vs. external-feeding guilds (predation sensitivity) and specialist- vs. generalist-insects.Surrounding vegetation of focal seedlings influences the abundance of insect herbivores and damage. Specialist insects (leaf miners) are affected by the understorey vegetation close to oak seedlings, decreasing with its presence or structural diversity. The damage caused by generalist insects depend on the large-scale composition of plant communities, and increase with tree species richness and cover or on conspecific forest habitats. Exclusion of insectivorous birds affects insect herbivory in a species-specific manner, and also greatly varies with forest habitats and presence of vegetation around focal plants. The indirect effect of bird predation on leaf damage is observed on seedlings beneath noncongeneric canopy trees. The removal of local surrounding vegetation affects the top-down effect of insectivorous birds on insect herbivores, according to their sensitivity to predation and the accessibility of preys. To conclude, our studies provide experimental evidences of interactive effects between bird predation and neighbouring vegetation on insect herbivores and levels of herbivory. These indirect effects are strongly related to the specialisation of herbivores and to their sensitivity to bird predation

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Valls, Fox Hugo. "To drink or not to drink? : the influence of resource availability on elephant foraging and habitat selection in a semi-arid savanna." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS130/document.

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L’eau et le fourrage sont deux ressources non substituables pour les herbivores dans les écosystèmes arides et semi-arides. La distribution spatiale de l’eau de surface détermine la distribution et l’abondance des espèces dépendantes de l’eau. Cependant les processus impliqués à l’échelle individuelle demeurent méconnus. Treize groupes familiaux d’éléphants d’Afrique (Loxodonta africana) et dix mâles ont été équipé de colliers GPS dans le parc National de Hwange, au Zimbabwe, et à sa périphérie. Les éléphants fourragent autour de multiples points centraux : ils visitent un point d’eau périodiquement toutes les 5h, 24h, 48h ou 72h et s’éloignent plus de l’eau lorsque ils font des trajets de plus longue durée. Pendant la saison sèche, la température augmente et les ressources fourragères s’épuisent à proximité de l’eau. Les groupes familiaux d’éléphants visitent les points d’eau plus souvent en augmentant la fréquence des trajets courts et en abandonnant les trajets de 72h. Cependant, ils parviennent à se rendre plus loin de l’eau pendant les trajets de 24h en augmentant la vitesse de déplacement. Ainsi les patrons de déplacement révèlent que les capacités de locomotion et de navigation des éléphants sont au cœur de leur stratégie d’adaptation à la saison sèche. Malgré cela, ces capacités sont rarement incluses dans les modèles d’approvisionnement dans des environnements hétérogènes. Pendant ces trajets, les groupes familiaux sélectionnent les zones de faible densité de points d’eau à des échelles multiples. La force de la sélection pour ces zones de faible densité augmente avec la longueur du trajet et au cours de la saison. Malgré le fait que l’importance des échelles spatiales soit bien établie dans la littérature, les contraintes associées à l’utilisation de multiples points centraux distribués de manière hétérogène dans le paysage ont été négligé alors que cette distribution détermine le degré d’épuisement des ressources fourragères et les rétroactions sur la sélection de l’habitat. J’ai aussi montré que la faune sauvage évite fortement le bétail et les humains qui les conduisent en périphérie d’une zone protégée pendant la saison des pluies. Cependant cet évitement décline au cours de la saison sèche en raison de l’assèchement des points d’eau et de la raréfaction des ressources fourragères. Les éléphants sont de plus en plus contraints par la distribution de l’eau de surface en saison sèche en raison de l’augmentation de leur besoins en eau tandis qu’ils tentent de maintenir leur approvisionnement en fourrage. Cette étude donne une évaluation quantitative de la contrainte en eau à l’échelle individuelle ainsi que les effets de la distribution en eau dans le paysage sur un grand herbivore. Ces résultats peuvent guider les politiques de gestion de l’eau dans un contexte d’aridification dû au changement climatique
Water and forage are key non-substitutable resources for herbivores in arid and semi-arid ecosystems. The distribution of surface water determines the distribution and abundance of water dependent animal species yet little is known about the processes involved at the individual level. Thirteen African savanna elephant family groups and ten bulls (Loxodonta Africana) were tracked with GPS collars within and on the outskirts of Hwange National Park, Zimbabwe. Elephants behave as multiple central place foragers: They visit waterholes periodically every 5h, 24h, 48h or 72h and travel further from water during longer trips. During the dry season, temperatures increase and forage becomes depleted closer to water. Elephant family groups visit waterholes more often by increasing the proportion of briefer trips and abandoning 72h trips. However, they forage further during 24h trips by increasing travelling speed. Elephant movement patterns revealed locomotional and navigational abilities are at the core of their coping strategies although they are seldom allowed to vary in most foraging models of animal's use of heterogeneously distributed resources. During these foraging trips, family herds select for areas with low waterhole density at multiple scales. Selection strength for low density areas increases with both distance to water and the advancement of the dry season. Although scaling effects are widely recognized, the effects of the spatial distribution of multiple central places constraining foraging have been ignored yet they determine depletion effects and their feedbacks on habitat selection. I also showed that wildlife strongly avoid livestock and people that herd them at the boundary of a protected area during the rainy season yet avoidance decreases during the dry season when foraging and drinking resources become scares. Elephants are increasingly constrained by surface water availability during the dry season as their drinking requirements increase while they strive to main their forage intake. This study provides quantitative assessment of individual water dependence and of landscape effects of surface water distribution on a large herbivore. These findings can inform surface water management in contexts of aridification resulting from climate change

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Radloff, Frans Gustav Theodor. "The ecology of large herbivores native to the coastal lowlands of the fynbos biome in the Western Cape, South Africa." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019.1/1178.

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Sagerman, Josefin. "Marine seaweed invasions : Impacts and biotic resistance in native ecosystems." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116788.

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Marine seaweeds constitute one of the most productive plant systems known on Earth and a rich fauna including juvenile fish and crustaceans is dependent on the habitats they form. Human influence on marine costal ecosystems has resulted in large scale changes to the abundance and distribution of species, where species introductions constitute an obvious part. The aims of this thesis were to 1) explore how non-native seaweeds impact on ecosystem functions (primary production and decomposition), and 2) study how interactions between non-native seaweeds and native communities affect invasion success. I used a combination of laboratory assays, outdoor mesocosms and field experiments. Paper I and II revealed that the impact on ecosystem functions were substantially different depending on the identity of the invader. The highly successful non-native red alga Heterosiphonia japonica had a large effect on community productivity. Due to the rapid growth of the invader, the primary production increased by more than four times in mixed species communities with the invader compared to communities with only native species. In contrast, the morphologically similar and equally successful non-native red alga Bonnemaisonia hamifera grew slowly and had no effect on community production. But B. hamifera produces a potent defense compound that deters native herbivores and reduces the growth of micro-organisms. As a direct or indirect effect of this chemical defense, the litter from B. hamifera decomposed considerably slower compared to native seaweed litter. Rapid growth and defense against predation are likely important in explaining how the two invaders have become successful in the invaded range. These results show that traits related to invasion success may determine impacts on native communities. Paper III shows that the rapidly growing invader H. japonica is avoided as food by native herbivores, which likely enables the invader to survive during colder seasons with sub-optimal growth conditions. In paper IV I found that competition from the native brown alga Fucus vesiculosus decreased growth of the non-native congener Fucus evanescens. Native herbivores caused more damage to the native competitor but it did not relieve F. evanescens from competitive pressure. Several native brown algae grow in the niche of F. evanescens, which may explain why the species only is growing sparingly in the invaded range. The results indicate that competition with native seaweeds have potential to reduce the success of non-native seaweeds in the new range. In summary, this thesis shows that non-native seaweeds differ strongly in their effect on ecosystem functions. Knowledge of which traits are present among abundant non-native species and how these traits relates to different effects may enable us to gain a better understanding of invasion impacts on native communities. The thesis also highlights that competitive interactions can be of importance for invasion success in seaweed communities.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

Alien-native trophic interactions: consequences for invasion success and ecosystem effects of invasions

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Ramos, Luiz Henrique Martinelli. "Epizootia de raiva na região leste do municipio de Campinas, SP de 2.000 a 2.002." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/309058.

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Orientador: Maria Rita Donalisio Cordeiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-13T08:12:06Z (GMT). No. of bitstreams: 1 Ramos_LuizHenriqueMartinelli_M.pdf: 2162773 bytes, checksum: 935e5e08be80a3056b13bd86a8c6c84d (MD5) Previous issue date: 2009
Resumo: A raiva é uma doença de grande importância em saúde pública e por causar grandes prejuízos sócio-econômicos. Poucos são os estudos sobre epidemiologia e epizootiologia da raiva que utilizam as ferramentas do geoprocessamento e Sistema de Informação Geográfica (SIG). Este estudo tem como objetivo caracterizar o perfil epizootiológico da raiva em Animais Domésticos de Interesse Econômico (ADIE), no município de Campinas, SP, nos anos de 2.000 a 2.002, transmitidos pelo morcego hematófago, desmodus rotundus, e estudar a distribuição espacial dos casos e as variáveis associadas à ocorrência de mortes de ADIE. Foram utilizados dados secundários provenientes da Secretaria Municipal de Saúde e do Escritório de Defesa Agropecuária da Secretaria Estadual da Agricultura e Abastecimento. Os registros de óbitos confirmados laboratorialmente e a localização de 10 abrigos de morcegos hematófagos foram georreferenciados por meio de GPS (Global Position System). Na região de ocorrência dos casos pertencente à área de abrangência do Centro de Saúde Taquaral foi aplicado um questionário aos proprietários de imóveis e coletadas informações sobre finalidade da propriedade, existência de abrigos de morcegos, tipo de abrigo, existência de habitações humanas com morcegos, periodicidade de vacinação e ocorrência de mortes de animais nos últimos 6 meses. Foi ajustado modelo de regressão logística múltipla, tendo-se como variável resposta os óbitos por raiva e como variáveis preditoras as coletadas nas entrevistas. Foram investigadas 730 propriedades, obtendo-se coeficiente de mortalidade de ADIE de 2,3 por 1.000 animais (N=8230), sendo que para os eqüídeos foi de 17,96 por 1.000 animais. Os resultados mostraram 25 dos 66 óbitos estavam localizados a menos de 3.000 metros de três abrigos de Desmodus sp. As propriedades de ocorrência dos óbitos dos animais e os abrigos de morcegos hematófagos localizavam-se próximo a rios e bairros povoados, expondo a população humana a risco de raiva. A totalidade dos abrigos foram do tipo artificial, reforçando a adaptação do morcego a este tipo de abrigo. A espécie bovina foi a mais acometida pela doença, seguida da eqüina, embora os coeficientes de mortalidade tenham sido maiores nestes últimos. A cobertura vacinal foi alta, mas em intervalos inadequados. As variáveis associadas estatisticamente aos óbitos foram a existência de abrigos de morcegos e ocorrência de mortes nos últimos 6 meses nas propriedades. Reforça-se a relevância de manter níveis adequados de cobertura vacinal de raiva em ADIE conforme preconizam os órgãos sanitários. A incorporação das ferramentas e técnicas de geoprocessamento mostra-se úteis na avaliação e controle de epizootias. A intersetorialidade dos órgãos públicos da saúde e agricultura propiciou vínculos com a comunidade e mostrou-se importante na promoção, prevenção e proteção da saúde pública e animal
Abstract: Rabies is a disease of great importance to public health and it causes great socialeconomical impairments. There are few studies that use geoprocessing tools and Geographic Information System (GIS) to research the epidemiology of rabies. This study is aimed at analyzing the epidemiological profile of rabies epizooty transmitted by the vampire bat to herbivores in Campinas city, Sao Paulo, between 2000 and 2002. Moreover, the space distribution of cases and the variables associated with the death of herbivores were also studied. Secondary data available at the City Health Secretary and at the Office of the Cattle and Farming Raising of the State Secretary of Agriculture and Supply were used in this study. The death registries confirmed by laboratories as well as the location of 10 vampire bat roosts were georeferred through GPS. The region where the registries were taken is located around Health Centers of Taquaral. The farm owners located around Health Centers of Taquaral neighborhood had to answer a questionnaire explaining the purpose of the property, existence of bat roosts, type of roost, existence of human permanent presence around bat roosts, periodicity of vaccination and occurrence of animal deaths within the past 6 months. A model of multiple logistic regression was adjusted. The deaths caused by rabies were classified as response variables and the ones collected during the interviews were classified as predictor variables. 730 properties were investigated, obtaining the coefficient of herbivore mortality of 2.3 out of 1000 animals (N=8230), and 17.96 out of 1000 animals for equines. The results showed that 25 of the 66 death registries were localized less than 3000 meters of three Desmodus roosts. The properties where the animal deaths occurred and roosts of vampire bats were located near rivers and populated neighborhoods, exposing human population to risk. The total number of roosts was artificial, stressing the adaptation of bats toward this type of roost. Bovine species was infected the most, followed by equine, although the mortality coefficients were greater in the latter group. The vaccine coverage was high, but the intervals were inappropriate. The variables statistically associated to the deaths were the presence of bat roosts and deaths in the property within the last 6 months. It is important to reinforce the relevance of maintaining proper levels of vaccine coverage in herbivores according to what is claimed by sanitary agencies. The incorporation of tools, as well as geoprocessing techniques, proves to be useful for the evaluation and epizooty control. The proximity between public health and agricultural agencies provided bonds with the community and proved to be important for the promotion, prevention and protection of the public and animal health
Mestrado
Epidemiologia
Mestre em Saude Coletiva

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Michels, Guilherme Heck. "Efeito da presença de búfalos (Bubalus bubalis L.) sobre a comunidade vegetal de uma floresta estacional no sul do Brasil e implicações para sua regeneração." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/17326.

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A herbivoria por grandes mamíferos é um fator decisivo no direcionamento de comunidades vegetais, influenciando o crescimento, sobrevivência e reprodução das plantas. Os ungulados, quando exóticos, podem impactar os ecossistemas diferentemente de herbívoros nativos, gerando maiores efeitos nas comunidades de plantas. Os objetivos deste estudo foram avaliar se a presença de búfalos (densidade de 1 animal/ha) impacta as assembléias de plântulas e de arbustos numa floresta estacional semidecídua no sul do Brasil, além de inferir consequências para a manutenção da comunidade vegetal. Para isso realizamos duas abordagens no município de Sentinela do Sul: na primeira, estabelecemos um experimento de exclusão de bubalinos (duração de 14 meses) e na segunda, comparamos três áreas com presença e protegidas desses herbívoros por três e dez anos. Em ambas as abordagens, registramos as seguintes variáveis ecológicas: riqueza, altura média de plantas, cobertura vegetal, diversidade (Shannon), e biomassa. No experimento de exclusão, nenhuma das variáveis apresentou diferenças significativas perante presença e ausência de búfalos (após 14 meses). Na comparação das três áreas as comunidades vegetais mostraram diferenças qualitativas (composição de espécies) no contraste presença versus dez anos de exclusão de búfalos, e as variáveis riqueza e altura média sofreram, respectivamente, significativos incremento e decréscimo. A diferença observada para o incremento de diversidade de zero a dez anos de exclusão foi marginalmente significativa e a compactação do solo apresentou decréscimo em função do tempo de exclusão do gado. Portanto , os resultados do presente trrabalho indicam que as manchas florestais não respondem à remoção de búfalos em baixas densidades no curto prazo e, na ausência de grandes herbívoros, a floresta tende a incrementar sua complexidade via aumento de riqueza e diversidade.
Herbivory by large mammals is a key factor in plant communities, and has effects on growth, survival and reproduction of plants. Ungulates, when exotic, impact ecosystems in a different way compared to the native ones, and may have a more pronounced effect on plant communities. In this study we evaluated buffalo (1 animal/ha density) impact on the seedling and shrub assemblages in a semideciduous seasonal forest in southern Brazil and checked if such impact would affect plant community maintainability. To address these aims we conducted two studies in Sentinela do Sul County: 1. we established a buffalo exclusion experiment (during 14 months) and 2. compared three areas with presence and protected against these herbivores for three and ten years. In both studies, we measured the following ecological variables: plant cover, richness, diversity (Shannon), biomass and average height. In the exclusion experiment, any ecological variable showed significant differences between buffalo presence and absence plots. When the three areas were compared, the communities showed qualitative differences (species composition) in the contrast presence versus ten years of buffalo exclusion, and richness and average height showed, respectively, increase and decrease. The difference observed for an increase of diversity between zero and ten years exclusion was marginally significant, and soil compactation showed retraction in relation to livestock exclusion time. We conclude that forest spots don’t answer in short-term to low densities buffalo removal and, in the absence of large herbivores, the forest tends to develop its complexity by richness and diversity increase, in a long-term basis.

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Nachtrieb, Julie Graham. "The impact of invertebrates to four aquatic macrophytes: Potamogeton nodosus, P. illinoensis, Vallisneria americana and Nymphaea mexicana." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9058/.

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This research investigated the impact of invertebrates to four species of native aquatic macrophytes: V. americana, P. nodosus, P. illinoensis, and N. mexicana. Two treatments were utilized on each plant species, an insecticide treatment to remove most invertebrates and a non-treated control. Ten herbivore taxa were collected during the duration of the study including; Synclita, Paraponyx, Donacia, Rhopalosiphum, and Hydrellia. Macrophyte biomass differences between treatments were not measured for V. americana or N. mexicana. The biomasses of P. nodosus and P. illinoensis in non-treated areas were reduced by 40% and 63% respectively. This indicated that herbivory, once thought to be insignificant to aquatic macrophytes, can cause substantial reductions in biomass.

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Kersch, Monica Frank. "Poda experimental de Chromolaena pungens (Asteraceae) e seus efeitos multitroficos." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316239.

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Orientador: Thomas Michael Lewinsohn
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Perturbações naturais ou antrópicas podem induzir mudanças fenotípicas nas plantas, que por sua vez podem influenciar herbívoros, predadores e polinizadores. Fatores abióticos, tais como nutrientes também podem influenciar a recuperação das plantas. Neste estudo investigamos o efeito de poda experimental em artrópodos associados a plantas rebrotadas em populações naturais de Chromolaena pungens (Asteraceae: Eupatoriae), uma planta subarbustiva, perene e nativa de cerrado. Os objetivos deste trabalho foram avaliar como o rebrote após corte raso ou poda parcial e o suprimento de nutrientes influenciam: (i) o crescimento vegetativo, (ii) a reprodução e os caracteres florais, (iii) a abundância de galhas, insetos folívoros, insetos sugadores e seus predadores; (iv) a comunidade de insetos endófagos associados e a incidência de seus parasitóides. O experimento seguiu um desenho de dois fatores em blocos, onde foram manipulados corte (controle, corte parcial e corte raso) e nutrientes (sem adição de nutrientes e com adição de nutrientes). Plantas cortadas na base foram menores, produziram menos folhas e capítulos, tiveram sua fenologia retardada em um mês em comparação com plantas controle ou de corte parcial. No entanto, a taxa de crescimento, a área foliar e o tamanho dos capítulos foram maiores em plantas submetidas a corte raso. Tais plantas sofreram maiores níveis de herbivoria foliar e destruição de sementes. Além disso, a abundância, a riqueza, a diversidade de espécies de endófagos associados a capítulos de plantas cortadas foram maiores do que em plantas controle ou parcialmente cortadas. Em conseqüência, a composição de espécies endófagas diferiu entre plantas submetidas a diferentes tipos de corte. Por isso, os resultados deste estudo são relevantes para o entendimento de interações inseto-planta em ambientes que sofrem perturbações naturais ou antrópicas recorrentes
Abstract: Natural or human-induced disturbances may promote plant phenotypic modifications, developmental and phenological changes which, in turn, may influence herbivores, predators and pollinators. Abiotic factors, especially nutrient availability, may also influence plant recovery. In this study, we evaluated plant regrowth and arthropod responses to experimental clipping plants in natural populations of Chromolaena pungens (Asteraceae: Eupatoriae), a perennial, native shrub in the Brazilian Cerrado. In particular, we assess how resprouting after severe or partial damage and nutrients influence: (i) vegetative regrowth; (ii) reproductive effort and floral traits; (iii) the abundance of galling, leaf-chewing and sap-sucking insects and their predaceous arthropods; (iv) endophagous insects and their parasitoids. The experiment followed a two-factor randomized block design, respectivelly clipping (control, partial clipping and basal clipping) and nutrients (no nutrient added and with nutrients added). Basally clipped plants were smaller, produced fewer leaves and flowerheads than partially clipped and control plants, moreover heir floral phenology was delayed by one month. However, the relative elongation rate, leaf area and flowerhead size were greater in basally clipped plants. These plants also suffered higher leaf herbivory and seed destruction. Moreover, the abundance, species richness and abundance of flowerhead endophages were higher in basally clipped plants than in the other treatments. Not surprisingly, species composition differed among clipping treatments. For this reason, these findings contribute to the knowledge of insect-plant interactions in recurringly disturbed habitats
Mestrado
Ecologia
Mestre em Ecologia

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Pais, Mara Patrícia. ""Artrópodos e suas relações de herbivoria como bioindicadores nos primeiros estágios de uma recomposição de floresta estacional semidecidual em Ribeirão Preto, SP"." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/59/59131/tde-29032005-105741/.

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Em 1998 iniciou-se no campus da USP de Ribeirão Preto, SP, um projeto recuperação florestal entitulado "Floresta da USP", com o propósito de recompor,numa área de 75 ha, a floresta estacional semidecidual, um dos tipos de vegetação nativa da região. O presente estudo teve como objetivo avaliar as principais modificações que se processam neste novo habitat nos primeiros anos seguidos ao plantio, utilizando a comunidade de artrópodos e as relações de herbivoria como bioindicadores. Inicialmente, foram avaliados alguns parâmetros da estrutura do habitat em quatro sub-áreas com idades diferentes, comparando-as com um remanescente de floresta nativa existente nas proximidades. Entre estes mesmos locais, foi comparada a comunidade de artrópodos epígeos através de análise multivariada, buscando relacioná-las com variáveis ambientais. Além disso, numa das áreas foi acompanhada a dinâmica da comunidade de artrópodos associada à seis espécies vegetais (três pioneiras e três tardias), por dois anos consecutivos. Nas mesmas espécies vegetais utilizadas para a amostragem de artrópodos, foram avaliados os níveis de herbivoria e algumas características vegetais que poderiam influenciar na preferência por insetos herbívoros. Ficou demonstrado que as maiores transformações do habitat recomposto ocorrem nos dois primeiros anos seguidos ao plantio. As principais variáveis do habitat relacionadas com a fauna de artrópodos epígeos foram a altura da vegetação, presença de gramíneas invasoras e presença de um terceiro estrato arbóreo, exclusivo da mata nativa. Apesar de muito dissimilares da comunidade da mata, as comunidades das sub-áreas da Floresta da USP mostram uma tendência de se aproximarem da existente na mata de acordo com o tempo transcorrido após o plantio. Em relação à fauna de dossel, embora não se tenha observado diferença na riqueza, abundância e diversidade geral entre os dois anos seguidos ao plantio, foi detectada uma grande dissimilaridade de espécies e uma profunda reestruturação da abundância de organismos dentro das guildas. As formigas, tanto por sua abundância como riqueza, tiveram grande participação dentro das diversas variáveis da comunidade analisadas e, entre elas, as formigas cortadeiras foram também responsáveis por uma grande elevação nos níveis de herbivoria do primeiro para o segundo ano de acompanhamento, tanto em espécies iniciais quanto tardias.
In 1998 a recomposition project named "Floresta da USP" was started at the USP campus in Ribeirão Preto, SP, aiming at recovering a 75 ha area with the regional native vegetation, the seasonal semideciduous forest. This study evaluated the main changes that ocurried in this new habitat during the first years after planting, considering the arthropod community and the herbivory relationships as bioindicators. We measured some habitat structure parameters at four sites of different ages, contrasting them to the same parameters measured at a local forest patch. The epigeous arthropod community was compared among sites using multivariate analysis, including several environmental variables. We also monitored the community dynamics of arthropods, herbivory levels and leaf physical chemical caracteristics of six plant species (3 pioneers and 3 late successional) at one of the sites during two years as well as the main leaf variables that could have some effect on the herbivore preferences. Results indicated great chances in the first years of recomposition. Vegetation height, presence of alien grasses, and presence of a third stratum at the forest patch were the principal habitat features related to the epigeous arthropod community. Despite the high dissimilarity, arthropod community of recomposed sites had a tendency of reducing this dissimilarity over time in relation to the forest. Richness, abundance, and diversity of canopy arthropod community were not different between the two years. However, a high species dissimilarity was detected and a strong guild rearrangement concerning abundance from one year to another. There was a high number of species and individuals. Leaf-cutting ants were important to the ecosystem dynamics due to the high levels of herbivory imposed to several plant species.

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Champagne, Émilie. "Communautés végétales et interactions plante-herbivore : comment l'espèce, la qualité nutritive et la répartition spatiale des plantes environnantes influencent le broutement par les grands herbivores." Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27778.

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Les interactions trophiques plante-herbivore sont indirectes lorsque la consommation d’une plante par un herbivore est influencée par la présence d’une plante voisine. L’influence des plantes environnantes sur la sélection des herbivores a été décrite par des études sur l’approvisionnement des herbivores, mais aussi par des études sur les effets associatifs entre plantes. À cause de leur évolution parallèle, certains thèmes communs dans les études sur l’approvisionnement des animaux ont eu peu d’échos dans la compréhension des effets associatifs entre les plantes. L’objectif général de cette thèse est de comprendre les effets indirects des communautés végétales sur l’utilisation des plantes par les grands herbivores, dans le contexte des facteurs affectant l’approvisionnement. Premièrement, je me suis intéressée à la distance à laquelle une plante environnante influence la sélection, car l’approvisionnement est un processus spatialement hiérarchique. Grâce à une méta-analyse, je révèle que les plantes environnantes influencent l’utilisation d’autres plantes par les grands herbivores jusqu’à des centaines de mètres carrés. En étudiant les effets associatifs à l’île d’Anticosti (Québec, Canada), je démontre que les plantes environnantes peuvent augmenter ou diminuer le broutement du cerf de Virginie sur le sapin baumier, selon l’échelle considérée. Deuxièmement, j’ai testé l’effet de facteurs susceptibles d’influencer l’approvisionnement des herbivores sur les effets associatifs. Par exemple, la qualité nutritive des plantes environnantes augmentait le broutement sur les sapins. De plus, l’abondance relative des plantes de la communauté pouvait créer des effets associatifs : en Outaouais (Québec, Canada), les pins blancs étaient moins broutés dans les parcelles plus diversifiées où l’abondance relative des espèces préférées était plus faible. Ma thèse met en valeur l’importance d’incorporer une perspective animale, qui tient compte des objectifs et des contraintes qui génèrent les choix des herbivores, à l’étude des effets associatifs. De plus, elle propose des avenues de recherches prometteuses, comme incorporer la variabilité intraspécifique dans les traits fonctionnels des plantes, tel que leur qualité nutritive, et considérer les effets associatifs à plusieurs échelles spatiales. Ces travaux améliorent notre compréhension des interactions trophiques indirectes, en démontrant l’influence de facteurs comme l’abondance des ressources sur ces interactions. De plus, je propose un mécanisme potentiel, soit les comportements d’approvisionnement des herbivores, ce qui ouvre la voie à une généralisation des effets associatifs à différents systèmes.
Plant-herbivore trophic interactions can be indirect, such as when the consumption of a plant by an herbivore is influenced by the presence of a neighbouring plant. The influence of neighbouring plants on herbivores’ selection has been described in studies of foraging but also in studies of associational effects between plants. Because of their parallel evolution, some common theme in the studies of animal foraging has been seldom addressed in the understanding of associational effects among plants. The general objective of this thesis is to understand the indirect effects of vegetation communities on plant use by large herbivores, in the context of factors affecting foraging. First, I investigated at which distance a neighbouring plant can influence herbivores’ selection, because foraging is a spatially hierarchical process. By a meta-analysis, I uncovered that neighbouring plant can influence the use of other plant species by large herbivores up to hundreds square metres. By a study of associational effects on Anticosti Island (Québec, Canada), I also demonstrated that neighbouring plants can increase or decrease browsing by white-tailed deer on balsam fir, depending on the scale considered. Second, I tested the relative contribution on associational effects of factors susceptible to influence foraging by herbivores. For example, the nutritional quality of neighbouring plants increased browsing on firs. Moreover, the relative abundance of plants in the community can generate associational effect: in the Outaouais region (Québec, Canada), white pines were less browsed in diversified plots where the relative abundance of preferred species was lower. My thesis supports the importance of incorporating an animal perspective, which takes into account the objectives and constraints on herbivores foraging choices, in the study of associational effects. Moreover, it offers promising research perspective, like including plant intraspecific variability in functional traits, such as nutritional value, and considering associational effects at multiple spatial scales. This work improves our understanding of indirect trophic interactions, by demonstrating the influence of factors such as resource abundance on these interactions. It also proposes a mechanism, foraging processes of herbivores, which paves the way to a generalization of associational effects in different systems.

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Fogelström, Elsa. "Herbivores, pollinators and selection on flowering time in tetraploid and octoploid Cardamine pratensis." Thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-88100.

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Repeated polyploidization events are thought to be among the most important causes of sympatric speciation throughout evolutionary time. Changes in phenology and trait expressions that arise in polyploids have been shown to affect plant interactions with insect herbivores and pollinators. If these interactions are changed, selection subsequent to the polyploidization event could contribute to further divergence, or increased similarity, of cytotypes. This study was conducted to investigate plant interactions with insect herbivores and pollinators and patterns of selection in tetraploid and octoploid Cardamine pratensis L. (Brassicaceae), and to answer the following questions: i) Is there phenotypic selection on flowering phenology and number of flowers? ii) Is pollen limitation or herbivory most important for variation in reproductive output? iii) During what stages of ovary and ovule development do variation in fitness mainly arise? iv) Can the intensity of interactions be linked to phenology and number of flowers, suggesting that selection is mediated by pollen limitation or herbivory? v) Do intensity of interactions, and of interaction-mediated selection, differ between ploidy levels? From a combination of an observational study of herbivory and a hand pollination experiment, selection was found for earlier flowering in both subspecies. Intensity of herbivory was an important determinant of plant reproductive success, while hand pollination had little effect. Positive effects of flowering time on intensity of herbivory suggest that selection for earlier flowering was mediated by herbivores. Tetraploids initiated flowering later and suffered from more intense herbivory than did octoploids. The direction of selection was similar in both subspecies. However, differences strength of selection and intensity of herbivory suggest that there is a possibility of selection for their further divergence.
Polyploidisering anses vara en av de viktigaste orsakerna till artbildning inom populationer. Skillnader i blomningskaraktärer, såsom fenologi och blomantal, som uppstår i och med polyploidiseringen har visat sig påverka växters interaktioner med såväl pollinatörer som herbivorer. Förändringar i växt-insektsinteraktioner till följd av polyploidiseringen kan leda till selektion för ökade skillnader, eller likheter, mellan cytotyper. Studiens syfte var att undersöka växters interaktioner med insekter i form av pollinatörer och herbivorer, samt att undersöka selektionsmönster hos tetraploida och oktoploida Cardamine pratensis L. (Brassicaceae). Jag ville även besvara följande frågor: i) Sker selektion på blomningstid och blomantal? ii) Vilken växt-insektsinteraktion är viktigast för variation i reproduktionsframgång? iii) Under vilka utvecklingsstadier uppstår den största variationen i fitness? iv) Kan intensiteten av interaktionerna kopplas till blomningsfenologi och blomantal, vilket skulle indikera att selektion förmedlas genom pollenbegränsning eller herbivori? v) Skiljer sig styrkan av interaktionerna, och av interaktionsförmedlad selektion, mellan ploidinivåer? Studien utformades som en kombination av en observationsstudie av herbivori och ett handpollineringsexperiment, och jag fann selektion för tidigare blomning hos de två underarterna. Reproduktionsframgång styrdes av herbivori snarare än pollenbegränsing. Förlust av potentiell fitness genom att fröämnen inte utvecklades till frön var den faktor som starkast påverkade variation i fitness, och detta var också den fas i utvecklingen som bidrog i störst utsträckning till kvantitativ förlust av fitness. Ett positivt samband mellan blomningsfenologi och herbivoriintensitet indikerar att selektion för blomningstid var förmedlad av herbivorer. Tetraploider blommade senare och utsattes för mer intensiva herbivorattacker än oktoploider. Detta, samt skillnader i selektionsstyrka, indikerar att selektion skulle kunna leda till ökad divergens av underarterna.

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Altfeld, Laura F. "Herbivore Abundance in Simple and Diverse Habitats: The Direct and Indirect Effects of Plant Diversity and Habitat Structure." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000062.

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Dissertations / Theses on the topic 'Herbivorie'

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