Dissertations / Theses: 'Niche (Ecology)'

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Cruz, Leonardo Dominici. "Nicho trofico de Gracilinanus microtarsus (Didelphimorphia: Didelphidae) : variação intra-populacional e inter-individual." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316227.

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Orientador: Sergio Furtado dos Reis
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A teoria do nicho ocupa uma posição central na Ecologia, tendo um papel fundamental nos modelos de dinâmicas populacionais e de comunidades. Apesar disso, sua formalização tradicional é baseada nos princípios da aproximação do campo médio e da lei da ação das massas, os quais presumem que os indivíduos de uma espécie são ecologicamente equivalentes e suas interações são proporcionais às suas densidades. Esta abordagem tem se mostrado inadequada em descrever as dinâmicas do nicho trófico, visto que tanto fatores endógenos quanto exógenos contribuem de forma significativa para a variação do nicho populacional. Desse modo o presente estudo teve como objetivo investigar a dieta, a dinâmica do nicho trófico populacional do marsupial Gracilinanus microtarsus (Wagner, 1842) em uma área de cerradão em São Paulo, assim como investigar a influência da variação inter-individual neste fenômeno. A dieta de G. microtarsus foi composta de invertebrados e frutos, com a predominância de insetos. As amplitudes de nicho trófico de machos e fêmeas foram maiores na estação quente-úmida do que na fria-seca. Entre os sexos, a amplitude do nicho de machos e fêmeas aparentemente não diferiu na estação quente-úmida. Na estação fria-seca, fêmeas apresentaram nichos mais amplos do que os machos. No nível individual, os nichos tróficos de machos e fêmeas foram similarmente proporcionais ao nicho de sua população. No entanto, esta similaridade foi maior na estação fria-seca. Nem o tamanho amostral, nem o número de categorias alimentares detectadas nas fezes influenciaram estes resultados. Isto indica que, no geral, os indivíduos de G. microtarsus se comportam de forma oportunística, utilizando os recursos de acordo com sua disponibilidade no ambiente
Abstract: The niche theory occupies a central position in the Ecology, having a fundamental role in the population and community dynamic models. Despite this, its traditional formalization is based on the principles of the mean-field and on the law of mass action, which presume that the individuals of a species are ecologically equivalent and their interactions are proportional to their densities. This approach is inadequate in describing the dynamics of trophic niche, since many endogenous and exogenous factors contribute significantly to the variation of the population niche. This study aimed to investigate the diet, the dynamics of the population trophic niche of the gracile mouse opossum Gracilinanus microtarsus (Wagner, 1842) in a ¿cerradão¿ area of São Paulo state, as well as to investigate the influence of the inter-individual variation in this phenomenon. The diet of G. microtarsus was composed of invertebrates and fruits, with the predominance of insects. The trophic niche width of males and females was higher in the warm-wet season than in the cool-dry season. Between sexes, the niche width of males and females did not differ in the warm-wet season and in the cool-dry season. Females presented larger niche width than males. At the individual level, the niches of males and females were similarly proportional to their populations. However, in the cool-dry season, this similarity was higher. Neither amostral size nor number of food resource types detected in faeces influenced these results. This indicates that, in general, the individuals of G. microtarsus behave as opportunistic foragers, using the resources in according to with their availability in the environment
Mestrado
Mestre em Ecologia

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Lima, Felipe Pontieri de [UNESP]. "Estrutura trófica das assembléia de peixes da represa de Jurumirim, alto rio Paranapanema-SP, Brasil." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/99409.

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Este estudo foi realizado na represa de Jurumirim, alto rio Paranapanema – SP, em três trechos limnologicamente distintos (lótico, transição e lêntico) e em duas lagoas marginais próximas a região de desembocadura do Rio Paranapanema na represa de Jurumirim. O objetivo foi avaliar os padrões relacionados a partilha de recursos alimentares e a estrutura e organização trófica das assembleias de peixes desta represa. Os peixes foram coletados bimestralmente com redes de espera entre abril/2009 e fevereiro/2010. Foram analisados conteúdos estomacais de 24 espécies distribuídas em três ordens e onze famílias quais consumiram no total 50 itens alimentares identificados dispostos em nove categorias tróficas, sendo que os itens principais foram fragmento vegetal, fragmento de peixes e detrito orgânico Os peixes foram classificados mediante a análise de similaridade de acordo com o item preferencial consumido sendo possível reconhecer oito guildas tróficas: Herbívoro, Detritívoro, Piscívoro, Detritívoro/Herbívoro, Insetívoro, Invertívoro e Carcinófago. A guilda dos herbívoros, detritívoros e piscívoros ocorreram em todos os trechos amostrados, sendo a composição em termos de espécie das guildas variável entre os trechos, com nove das 24 espécies estudadas ocorrendo em guildas distintas, indicando flexibilidade na dieta destas espécies. As assembleias de peixes da represa de Jurumirim apresentaram em sua maioria baixos valores de amplitude e sobreposição de nicho trófico, indicando que esta comunidade de peixes partilha os recursos alimentares. Portanto é possível concluir que a ictiofauna da represa de Jurumirim apresenta uma estrutura trófica bem estabelecida, qual as espécies partilham recursos alimentares de forma a evitar competição pelos recursos disponíveis
This study was carried in the Jurumirim Reservoir, Upper Paranapanema River, -SP in three distinct limnologic stretches (lotic, transition, lentic) and two marginal lagoons near the mouth of the Paranapanema river in the Jurumirim Reservoir. The aim was to evaluate the patterns related to food resources partitioning, as well as the trophic structure and organization of fish assemblages. Fish were collected bimonthly with gill nets between April/2009 and February/2010. The stomach contents of 24 species were analyzed, in three orders and eleven families which consumed a total of 50 identified food items arranged in nine trophic categories, with vegetal matter, fragment of fish and organic detritus waste as the main items in the diet of species. Fish were classified by the similarity analysis according to the preferential item consumed, and eight trophic guilds were recognized: herbivorous, detritivorous, piscivorous, detritivorous/herbivorous, insectivorous, invertivorous and carcinophagous. The guild of herbivorous, detritivorous and piscivorous occurred in all sampling sites. The species composition of trophic guilds was variable among sites, with nine of the 24 studied species occurring in different guilds, indicating flexibility in the diet of this species. The fish assemblage of Jurumirim Reservoir showed low niche breadth niche overlap values, indicating that this fish community share food resources. Therefore we conclude that the fish fauna of the reservoir Jurumirim has a well-established trophic structure, which species partitioning food resources to avoid competition

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Lima, Felipe Pontieri de. "Estrutura trófica das assembléia de peixes da represa de Jurumirim, alto rio Paranapanema-SP, Brasil /." Botucatu, 2012. http://hdl.handle.net/11449/99409.

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Orientador: Edmir Daniel Carvalho
Coorientador: Ana Paula Vidotto-Magnoni
Banca: Edmir Daniel Carvalho
Banca: Rosemara Fugi
Banca: Sirlei Therezinha Bennemann
Resumo: Este estudo foi realizado na represa de Jurumirim, alto rio Paranapanema - SP, em três trechos limnologicamente distintos (lótico, transição e lêntico) e em duas lagoas marginais próximas a região de desembocadura do Rio Paranapanema na represa de Jurumirim. O objetivo foi avaliar os padrões relacionados a partilha de recursos alimentares e a estrutura e organização trófica das assembleias de peixes desta represa. Os peixes foram coletados bimestralmente com redes de espera entre abril/2009 e fevereiro/2010. Foram analisados conteúdos estomacais de 24 espécies distribuídas em três ordens e onze famílias quais consumiram no total 50 itens alimentares identificados dispostos em nove categorias tróficas, sendo que os itens principais foram fragmento vegetal, fragmento de peixes e detrito orgânico Os peixes foram classificados mediante a análise de similaridade de acordo com o item preferencial consumido sendo possível reconhecer oito guildas tróficas: Herbívoro, Detritívoro, Piscívoro, Detritívoro/Herbívoro, Insetívoro, Invertívoro e Carcinófago. A guilda dos herbívoros, detritívoros e piscívoros ocorreram em todos os trechos amostrados, sendo a composição em termos de espécie das guildas variável entre os trechos, com nove das 24 espécies estudadas ocorrendo em guildas distintas, indicando flexibilidade na dieta destas espécies. As assembleias de peixes da represa de Jurumirim apresentaram em sua maioria baixos valores de amplitude e sobreposição de nicho trófico, indicando que esta comunidade de peixes partilha os recursos alimentares. Portanto é possível concluir que a ictiofauna da represa de Jurumirim apresenta uma estrutura trófica bem estabelecida, qual as espécies partilham recursos alimentares de forma a evitar competição pelos recursos disponíveis
Abstract: This study was carried in the Jurumirim Reservoir, Upper Paranapanema River, -SP in three distinct limnologic stretches (lotic, transition, lentic) and two marginal lagoons near the mouth of the Paranapanema river in the Jurumirim Reservoir. The aim was to evaluate the patterns related to food resources partitioning, as well as the trophic structure and organization of fish assemblages. Fish were collected bimonthly with gill nets between April/2009 and February/2010. The stomach contents of 24 species were analyzed, in three orders and eleven families which consumed a total of 50 identified food items arranged in nine trophic categories, with vegetal matter, fragment of fish and organic detritus waste as the main items in the diet of species. Fish were classified by the similarity analysis according to the preferential item consumed, and eight trophic guilds were recognized: herbivorous, detritivorous, piscivorous, detritivorous/herbivorous, insectivorous, invertivorous and carcinophagous. The guild of herbivorous, detritivorous and piscivorous occurred in all sampling sites. The species composition of trophic guilds was variable among sites, with nine of the 24 studied species occurring in different guilds, indicating flexibility in the diet of this species. The fish assemblage of Jurumirim Reservoir showed low niche breadth niche overlap values, indicating that this fish community share food resources. Therefore we conclude that the fish fauna of the reservoir Jurumirim has a well-established trophic structure, which species partitioning food resources to avoid competition
Mestre

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Araújo, Marcio Silva. "Variação interindividual no uso de recursos em populações naturais : novos padrões e implicações." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316223.

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Orientadores: Sergio Furtado dos Reis, Glauco Machado
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A teoria ecológica clássica, em especial a teoria de nicho, foi construída sob a suposição de que os indivíduos de uma população são equivalentes em termos da utilização de recursos. Entretanto, é sabido que os indivíduos de uma população podem variar no uso de recursos e que essa variação pode ter importantes implicações ecológicas e evolutivas. Essa variação interindividual pode dar origem a morfotipos discretos (¿polimorfismo de recursos¿) ou ser contínua (¿especialização individual¿). O presente estudo teve como objetivo investigar a variação interindividual no uso de recursos em quatro populações de rãs do Cerrado brasileiro (Leptodactylus sp., L. fuscus, Eleutherodactylus cf. juipoca e Proceratophrys sp.), uma população de vespas-caçadoras de uma área de Mata Atlântica (Trypoxylon albonigrum) e uma população do peixe lacustre Gasterosteus aculeatus da Columbia Britânica, Canada. Houve evidência de variação interindividual em todas as populações estudadas, indicando que esse fenômeno não é exclusivo de comunidades temperadas de baixa diversidade. Houve uma associação entre a amplitude dos nichos populacionais e o grau de variação interindividual, indicando que os nichos individuais permanecem estreitos apesar da expansão do nicho populacional. Esse padrão é consistente com a presença de trade-offs funcionais associados ao uso dos recursos. A base dos trade-offs permanece desconhecida no caso das rãs e das vespas, mas é provavelmente comportamental. No caso de G. aculeatus, os trade-offs têm base morfológica, mas são mediados pelo comportamento. Além disso, foi identificado um padrão de partição de recursos inédito nesses peixes, em que os indivíduos formam microguildas que representam subdivisões dos recursos litorâneos e pelágicos. São propostos dois novos métodos para a investigação da variação intrapopulacional no uso de recursos, um deles baseado no uso de isótopos estáveis de carbono (d13C) e o outro na teoria de redes complexas
Abstract: Ecological theory, and specially niche theory, was built on the assumption that individuals are equivalent in terms of resource use. However, the individuals in a population may vary in their resources, and this interindividual variation may have important ecological and evolutionary implications. Such variation may give rise to discrete morphological groups (¿resource olymorphism¿) or it may be more continuous (¿individual specialization¿). In the present study, we investigated interindividual variation in resource use in four populations of frogs inhabiting the Brazilian Cerrado (Leptodactylus sp., L. fuscus, Eleutherodactylus cf. juipoca e Proceratophrys sp.), one population of hunting-wasp of the Atlantic Rainforest (Trypoxylon albonigrum), and one population of sticklebacks (Gasterosteus aculeatus) from British Columbia, Canada. We found evidence of interindividual diet variation in all studied populations, indicating that such variation is not restricted to temperate, depauperate comunities. There was an association between niche width and the degree of interindividual variation, indicating that individual niches remain constrained as the population niche expands. This pattern is consistent with the presence of functional trade-offs associated with resource use. In the case of the frogs and the wasps, the nature of the trade-offs remains unknown, but are likely to be behavioral. In the sticklebacks, the trade-offs have a morphological basis, but are mediated by behavior. We found that individual sticklebacks partition resources within littoral and within pelagic prey, which represents a finer pattern of resource partitioning than the traditional ¿littoral-pelagic¿ dichotomy. Two new methods for the quantification of interindividual diet variation are proposed, one based on carbon stable isotopes (d13C) and another based on complex-network theory
Doutorado
Ecologia
Doutor em Ecologia

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Fromant, Aymeric. "The ecology and niche segregation of diving petrels." Thesis, La Rochelle, 2022. https://tel.archives-ouvertes.fr/tel-03959129.

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L'exploration de la niche écologique d'une espèce implique une analyse à plusieurs échelles, car différentes contraintes environnementales peuvent avoir des conséquences écologiques importantes. Cependant, l'absence d'informations précises sur l'écologie des petites espèces de procellariiformes a considérablement limité leur étude, impactant notre capacité à définir une planification de conservation appropriée. Les avancées technologiques dans la miniaturisation des enregistreurs de données permettent depuis peu de collecter des données écologiques sur ces espèces. Dans cette étude, une approche multidisciplinaire a été utilisée pour étudier la niche écologique des pétrels plongeurs communs et de Géorgie du Sud. Les principaux objectifs étaient de : 1) décrire leur écologie alimentaire pendant les périodes de reproduction et de non-reproduction, et étudier leurs variations interannuelles ; 2) déterminer les différences écologiques entre les populations de l'Océan Austral ; et 3) étudier les variations de leur écologie tout au long du cycle annuel dans un contexte de ségrégation écologique entre ces deux espèces sœurs. Les résultats ont démontré que les pétrels plongeurs présentent des capacités de vol remarquables malgré leur charge alaire élevée, se nourrissant sur de vastes zones pendant la reproduction et migrant à plusieurs milliers de kilomètres de leur colonie pendant la période post-reproduction. Ces analyses ont révélé d'importantes différences écologiques au sein des espèces, notamment en termes de phénologie et de zone de migration. La collecte de données sur plusieurs années a considérablement renforcé ces résultats et fournit des informations précieuses pour comprendre les limites des niches écologiques des pétrels plongeurs. Enfin, la variation de ségrégation en fonction du stade de reproduction a démontré l'importance d'une approche multi-outils pour mieux décrire et comprendre la coexistence d'espèces écologiquement similaires
Exploring a species’ ecological niche entails investigating at multiple scales, as different environmental threats and niche constraints between intra-species levels may lead to important ecological and conservation consequences. However, the absence of precise information about small procellariiform species ecology has greatly limited ecological niche modelling studies, directly impacting our ability to delineate proper conservation planning. Technological advancements in the miniaturisation of data loggers have made it possible to collect ecological data of such species. In the present study, a multi-tooled approach was used to investigate the ecological niche of the common and the South-Georgian diving petrels. The primary objectives were to: 1) describe their foraging ecology during the breeding and non-breeding periods, and investigate their inter-annual variations; 2) determine the ecological differences between populations throughout the Southern Ocean; and 3) study the variations in their foraging ecology throughout the entire annual-cycle in the context of niche segregation between two sibling species. The results demonstrated that diving petrels exhibit remarkable flying abilities despite their high wing loading, foraging over large areas during the breeding season, and migrating several thousands of kilometres from their colony during the post-breeding period. These analyses revealed important ecological differences throughout the species distribution, particularly in terms of phenology and migration area. Collecting data over several years substantially strengthens results and provides valuable information to understand the variations and the limits of diving petrel ecological niches. Finally, a stage-dependent and context-dependent niche segregation analysis demonstrated the importance of a multi-tooled approach to better describe and understand the co-existence of ecologically similar species

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Page, Brad. "Niche partitioning among fur seals /." Access full text, 2005. http://www.lib.latrobe.edu.au/thesis/public/adt-LTU20060622.153716/index.html.

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Thesis (Ph.D.) -- La Trobe University, 2005.
Submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the Zoology Dept., School of Life Sciences, Faculty of Science, Technology and Engineering. Research. Includes bibliographical references (leaves 133-152). Also available via the World Wide Web.

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Rettig, Adam V. "Associations between benthic fishes and habitat at multiple spatial scales in headwater streams of the Missouri Ozarks /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418059.

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Kylafis, Grigorios. "Niche construction, facilitation and their ecological and evolutionary consequences." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97086.

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Organisms modify their environment through their activities and by doing so, they modify evolutionary pressures acting on them, as well as the ecological conditions under which they grow and reproduce. Niche construction, as defined by Odling-Smee et al. (2003), is a concept that captures the reciprocal organism-environment interaction from an evolutionary perspective. However, niche construction in the sense of biotically-driven improvement of the ecological environment has been poorly explored to date. I derive a consumer-resource model to investigate the consequences of niche construction for its agent. I show that niche construction is a mechanism by which a species enhances its ecological persistence, via positive ecological feedbacks, and partially regulates its environment against external changes, via adaptive feedbacks. Next, I integrate niche construction into traditional competition models. A species that improves the level of a limiting niche factor via niche construction simultaneously competes with adjacent species via deteriorating impacts on the level of the same or other limiting niche factors. I observe that the interplay between niche improving and niche deteriorating impacts modifies the potential for species coexistence. Moreover, I show that the niche constructing species has a facilitative effect on the equilibrium abundance of its competitor. The prevalence of the facilitative effect, however, depends on both species' competitive hierarchies and the fertility of the ecosystem. Finally, I derive a model to investigate the evolution of the strength of facilitation between two competing species, when one species improves abiotic conditions to the advantage of its competitor but without any benefit to itself. In this case, I predict that high strength of facilitation evolves in productive ecosystems. Overall, my thesis provides a novel framework for the investigation of niche improving and niche deteriorating impacts and their combined effects on species coexistence, community structure and ecosystem functioning.
Par leurs activités, les êtres vivants changent leur environnement, modifiant ainsi les pressions évolutives qui les affectent, ainsi que les conditions écologiques présidant à leur croissance et leur reproduction. Telle que définie par Odling-Smee et al (2003), la construction de niche est un concept qui recouvre l'interaction réciproque entre l'organisme et son environnement selon une perspective évolutive. Cependant, la notion de construction de niche comme amélioration de l'environnement écologique par les êtres vivants est encore peu explorée. J'ai construit un modèle d'un consommateur et de sa ressource, afin d'explorer les conséquences de la construction de niche sur l'agent de cette construction. J'ai montré que la construction est un mécanisme grâce auquel une espèce persiste plus longtemps dans l'écosystème, via des feedbacks écologiques positifs, et régule son environnement face aux changements externes, via des feedbacks adaptifs. Par la suite, j'ai intégré la construction de niche à des modèles traditionnels de compétition. Une espèce qui, par construction de niche, augmente le niveau d'un facteur limitant, entre simultanément en compétition avec les espèces voisines par sa détérioration du niveau de ce facteur ou d'autres facteurs limitants. J'ai constaté que ce jeu entre impacts positifs et négatifs sur la niche écologique modifie le potentiel de coexistence entre les espèces. De plus, j'ai montré que l'espèce qui construit sa niche a un effet facilitateur sur l'abondance de son compétiteur à l'équilibre. Cependant, l'importance de cet effet facilitateur dépend de la hiérarchie entre les capacités compétitives des deux espèces et de la productivité de l'écosystème. Enfin, j'ai construit un modèle pour examiner comment évolue l'intensité de la facilitation entre deux espèces en compétition, lorsqu'une des espèces améliore les conditions abiotiques pour l'autre espèce, sans aucun bénéfice pour elle-même. Dans ce cas, je prédis l'évolution d'un effet de facilitation fort dans les écosystèmes productifs. Globalement, ma thèse fournit un cadre de travail nouveau pour explorer les impacts amélioratifs et détérioratifs de la construction de niche, ainsi que leurs effets combinés sur la coexistence des espèces, la structure des communautés et le fonctionnement des écosystèmes.

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Sackmann, Brandon S. "Remote Assessment of 4-D Phytoplankton Distributions off the Washington Coast." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SackmannBS2007.pdf.

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Wisheu, Irene Catherine. "Shared preference niche organization: Implications for community organization and diversity." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9578.

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Patterns of resource partitioning have been widely described, but the causes of these patterns are incompletely understood. To explore how the patterns are formed, I did a quantitative literature survey. In Chapter One, I (1) discuss current misconceptions in the literature, (2) document and describe five ways in which resource partitioning can occur, and (3) establish guidelines for predicting the two most common ways in which patterns of partitioning are formed. In Chapter One, the most common way in which patterns of resource partitioning were formed was through shared preference niche organization. Centrifugal organization extends shared preference organization from one resource gradient to multiple gradients. In Chapter Two, experimental evidence supporting the validity of the centrifugal organization model is reviewed and predictions of the model are presented. The centrifugal organization model predicts how the size of species pools changes along a resource gradient. Two other models from the literature make contradictory predictions. The three models were tested in Chapter Three using biomass/species composition data from 33 eastern North American wetlands. The resulting 640 quadrats produced a pattern of pool size consistent with a previously untested model, the species pool model. This model states that the pattern of pool size is the same as the pattern of alpha diversity along a biomass gradient. This suggests that (1) the more easily measured alpha diversity values can be used to predict where large species pools occur and (2) ecological processes that are associated with changes in alpha diversity may also influence the species pool.

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Rolek, Brian William Hill Geoffrey E. "Microhabitat associations of wintering birds in a southeastern bottomland forest within the easter Gulf coastal plain of Florida." Auburn, Ala., 2009. http://hdl.handle.net/10415/1795.

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Dougherty, Ryan Fitzgerald. "Ecology and niche characterization of the invasive ornamental grass Miscanthus sinensis." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50989.

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The recent trend in bioenergy feedstock development focuses on the use of large-statured perennial grasses that pose a relatively high risk of becoming invasive species due to the similarity in desirable agronomic traits with those of many of our worst invaders. Thus, it would be prudent to evaluate the potential ecological benefits and consequences of widespread cultivation of potentially invasive species. Miscanthus sinensis and its sterile daughter species, Miscanthus × giganteus, are two prominent bioenergy feedstock candidates due to their low input requirements and significant biomass production in a broad range of growing conditions. Despite being an extremely popular ornamental grass, and naturalizing in over half of US states, little is actually known about the biology, ecology and niche requirements of M. sinensis. Thus, the objective of our research is to characterize extant M. sinensis populations, and evaluate the niche requirements, especially in terms of the commonly limiting resources of light and soil moisture. In order to better assess the risk of M. sinensis (and subsequently M. × giganteus) cultivation, we surveyed 18 naturalized populations across the east coast to characterize habitat preferences, population structure, and plant performance across a latitudinal gradient. We found the vast majority of M. sinensis populations occurred in areas of high and low resource availability (e.g. soil nutrients and light) along roadsides and forest edges, with outlier individuals found in forest understories. We conducted a greenhouse study to compare shade and soil moisture tolerance among common ornamental cultivars and naturalized populations, where we found enhanced plant growth and vigor in naturalized biotypes compared to ornamentals across varying levels of shade. We also found that both naturalized and ornamental biotypes were not significantly affected by soil moisture stress, and thus express significant drought tolerance. Finally, we investigated the temperature and moisture requirements of M. sinensis seeds and determined a base temperature of approximately 8"C, as well as variable moisture and time to germination requirements between varieties and seed sources. These basic ecological studies will help refine and support future evaluations and weed risk assessments of both Miscanthus sinensis and M. × giganteus, which is critical in prevention of major ecological invasions.
Master of Science in Life Sciences

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Bourguignon, Thomas. "The Anoplotermes group in French Guiana :systematics, diversity and ecology." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210132.

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Les termites forment un groupe animal important en milieu tropical, où leur richesse spécifique est plus élevée que dans n’importe quel autre écosystème. Ils se nourrissent de matière organique végétale à différent état de décomposition, du bois dur à la matière organique minérale du le sol. Cette diversification du régime alimentaire ne se produit que chez les Termitidae, parfois appelés « termites supérieurs », alors que les autres familles se nourrissent exclusivement de bois ou d’herbe. Les termites humivores sont extrêmement abondants en Amérique du Sud et en Afrique tropicale, mais sont relativement peu étudiés par rapport aux termites xylophages. C’est particulièrement vrai pour le groupe Anoplotermes, qui représente le groupe de termites le moins bien connu. Ce travail vise à faire la lumière sur l’écologie et la diversité de ce groupe strictement humivore, et comprend les sections suivantes :(1) Des échantillonnages standardisés dans sept sites de Guyane Française ont révèle, avec quelques exceptions, que les termites xylophages sont relativement peu spécialisés à un site. Au contraire, les espèces du groupe Anoplotermes, ainsi que les termites humivores en général, sont spécialisés à un type de forêt. Cette spécialisation contribue plus que probablement à la diversification écologique, et donc, à une augmentation de la richesse spécifique des termites humivores. (2) En utilisant les ratios d’isotopiques δ13C et δ15N, nous avons aussi trouvé qu’il existe une spécialisation des espèces le long d’un gradient d’humification chez le groupe Anoplotermes, de l’interface entre le bois pourri et le sol au sol pauvre en matière organique. Donc, au moins deux facteurs favorisent la richesse spécifique du groupe Anoplotermes dans le sol, malgré le manque d’évidence pour une séparation spatiale et temporelle entre les espèces. Cette spécialisation spécifique réduit la compétition interspécifique aux espèces se nourrissant de matière organique au même état de décomposition. (3) Ce mécanisme n’est probablement pas restreint aux espèces du groupe Anoplotermes et le ratio isotopique δ15N varie considérablement entre les termites humivores de manière générale. Les termites humivores comptent des espèces avec des régimes alimentaires différents ne partageant pas toujours les mêmes niches écologiques. Cette diversification du régime alimentaire ne c’est pas produit de manière aléatoire durant l’évolution des termites et les espèces proches tendent à se nourrir du même substrat. (4) Au niveau intraspécifique, il semble que la compétition contraigne la dynamique des colonies. En effet, chez A. banksi, nous avons trouvé que les nids matures sont surdispersés. Les nouveaux nids se trouvent principalement à une certaine distance des nids établis, plus particulièrement dans les trous laissés par les nids morts. Si ce patron est le résultat d’une sélection des sites de nidification, ou plutôt d’une exclusion compétitive reste sujet à discussion, mais met néanmoins en évidence la présence de compétition chez les termites humivores du groupe Anoplotermes. (5) Au vu de la richesse spécifique locale du groupe Anoplotermes, le nombre d’espèces décrites reste remarquablement bas. Après inspection du matériel type, seuls 30 espèces du groupe se sont avérés valides en Amérique du Sud, alors que 80% des espèces que nous avons collectées sont nouvelles pour la science. Cette disproportion entre ce qui est connu et la diversité réelle du groupe, met en évidence le besoin de réaliser des études supplémentaires pour améliorer la connaissance de ce groupe peu connu, le groupe Anoplotermes.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Costa, João Carlos Lopes. "Nicho trofico de Tropidurus hispidus (Sauria: Tropiduridae) em ambiente de restinga." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316377.

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Orientadores: Sergio Furtado dos Reis, Marcio Silva Araujo.
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A dieta é um dos principais atributos do nicho ecológico de qualquer espécie animal. Geralmente nos estudos ecológicos os indivíduos de uma população são considerados ecologicamente equivalentes em relação ao uso de recurso. Contudo, esta abordagem tem se mostrada inadequada na descrição da utilização de recurso para várias espécies, como demonstrado por dados empíricos. A variação intrapopulacional pode ser ocasionada por fatores exógenos ou fenômenos endógenos ocasionados pelas diferenças sexuais e/ou ontogenéticas. Além disso, indivíduos pertencentes à mesma classe etária, ao mesmo sexo e dentro da mesma localidade podem também exibir variação no nicho. Esse fenômeno é denominado de "especialização individual" e sua ocorrência tem sido descrita para comunidades temperadas ou depauperadas até o presente momento. Para verificar quais fenômenos podem produzir a variação no nicho de lagartos tropicais foi utilizado como modelo Tropidurus hispidus. Os objetivos deste estudo foram: descrever a composição da dieta; investigar a existência de variação intrapopulacional no nicho trófico; determinar em que níveis essa variação se expressa; e testar se a morfologia é um mecanismo subjacente ao uso de recursos alimentares nesta espécie. Dentre os fenômenos analisados, a variação intrapopulacional parece ser ocasionada unicamente pela especialização individual. Os itens mais consumidos por T. hispidus, formigas, besouros e cupins, produzem uma variedade de substâncias químicas tóxicas que podem impor um alto custo para desintoxicação e gerar preferências alimentares individuais. Outra possível fonte de variação é a ocorrência de diferentes comportamentos de forrageio por indivíduos da mesma população. Este é o primeiro registro da ocorrência de especialização individual em lagartos tropicais e reforça a percepção de que esse fenômeno esta presente em comunidades tropicais de alta diversidade, contrariando o padrão estabelecido na literatura, relacionando à ocorrência da especialização individual a comunidades temperadas e depauperadas.
Abstract: The diet is one of the main atributes of the ecological niche of animal species. Generally, the individuals of a population are considered ecologically equivalent in ecological studies that focus on resource use. Nevertheless, this approach has been inadequate to correctly describe resource use by various species, as demonstrated by empirical data. Intrapopulation variation may be caused by exogenous factors or endogenous phenomena such as sexual and/or ontogenetic differences. Additionally, individuals belonging to the same age or sex, and within a single site or time can also show differences in niche. This phenomenon has been defined as "individual specialization" and its occurrence is related to temperate and/or depauperate communities. To verify which phenomena produce niche variation in tropical lizards, we used Tropidurus hispidus as a model system. The aims of this study were to describe the diet composition; to investigate the existence of intrapopulational variation in trophic niche; to determine at which levels this variation is expressed, and test if the morphology is an underlying mechanism in food resource use in this species. The intrapopulation variation seems to be caused uniquely by individual specialization. The most consumed items by T. hispidus, ants, beetles and termites, produce a variety of toxic chemical substances that can impose a high cost for desintoxication and generate individual alimentary preferences. Another possible source of variation is the occurrence of different forage behaviors by individuals of the same population. This is the first record of the occurrence of individual specialization in tropical lizards, which suggests the presence of this phenomenon in highly diverse tropical communities, contradicting the established literature relating the occurrence of individual specialization to temperate and depauperate communities.
Mestrado
Mestre em Ecologia

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Kaspari, Michael Edward. "Niche relationships in an assemblage of neotropical granivorous ants." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186076.

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Ants are key players in ecosystem function, especially in the tropics, yet little is known about the diversity and behavior of tropical ant communities. In a lowland wet forest of La Selva, Costa Rica ants are the primary predators of over a third of the sizes of bird-dispersed seeds. Dominated by the tribes Attini, Pheidolini and Solenopsidini, 35-38 species of ant preyed on seeds or seed baits. This is the most diverse granivorous ant community yet recorded, with the high diversity associated with higher population densities, smaller colony sizes and smaller body sizes than North American granivorous ant communities. The size of a frugivore dropping is isometric with the size of the bird producing it, and decreases with rain. Ant predation on these droppings was highly variable in time and space. Discovery and recruitment to droppings increased with dropping size as predicted by simple models. However, partial predation of large droppings produced the highest seed mortality at intermediate-size droppings. Seeds were found in 29% of meter-square samples of ant nests, suggesting seed rain was not highly localized. Small droppings were used by the greatest variety of species--this corresponded to observations of ant aggression at the largest droppings. Niche breadth increased with body size for both seed size and microclimate. Large ants foraged in a greater range of Vapor Pressure Deficits than small ants, as predicted by the law of surface area to volume. Large ants also took a greater variety of seed sizes than small ants, aided through intraspecific size matching in the large species (mostly attines). The tendency for small ant species to have niches nested within those of large ant species highlights the need to understand how body size and colony size influence interactions in ant communities.

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Troia, Matthew John. "A mechanistic framework for understanding prairie stream fish distributions." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17285.

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Doctor of Philosophy
Department of Biology
Keith B. Gido
A fundamental goal of ecology is to understand environmental associations of species. These associations can provide a basis for predicting spatial distributions in contemporary habitats as well as how those distributions might change in response to anthropogenic environmental change. Developing species distribution models is limited by an incomplete understanding of functional traits, spatial scaling, and the mechanisms and generalities of correlations among abundance and environmental gradients. I address these four issues using observational and experimental approaches. First, I tested opposing mechanisms of community assembly by measuring the dispersion (i.e., diversity) of three types of functional strategies at three spatial scales and along environmental gradients. I found that communities are assembled via abiotic environmental filtering, but the strength of this filtering depends on the spatial scale of investigation, longitudinal network position, and type of functional strategy. Second, I quantified community-environment relationships across thirteen sub-basins, nested within the three major basins within Kansas to evaluate the consistency (i.e., generality) in predictive capability of environmental variables among sub-basins and across spatial extents. I found that longitudinal network position is consistently the strongest predictor of community composition among sub-basins, but in-stream and catchment predictors become stronger correlates of community composition with increasing spatial extent. Third, I used environmental niche models to quantify distributions of four pairs of congeneric cyprinids and found that species within each pair exhibited contrasting stream-size preferences. I then used field experiments to test for differences in individual-level performance between one pair of species (Pimephales notatus and P. vigilax) along a gradient of stream size. I found that adult spawn success and juvenile growth and condition increased with stream size for both species, indicating that these congeners respond similarly to abiotic gradients associated with the river continuum. I concluded that complementary distributions are a consequence of biotic interactions, differential environmental filtering evident in an unmeasured performance metric, or differential environmental filtering by an environmental factor operating at longer timescales. These studies demonstrate the context dependencies of characterizing habitat associations of stream fishes, but also reveal the general importance of stream size and associated environmental gradients in structuring stream fish communities.

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Page, Brad, and page bradley@saugov sa gov au. "Niche partitioning among fur seals." La Trobe University. Zoology Department, School of Life Sciences, 2005. http://www.lib.latrobe.edu.au./thesis/public/adt-LTU20060622.153716.

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At Cape Gantheaume, Kangaroo Island (South Australia), adult male, lactating female and juvenile New Zealand (NZ) and Australian fur seals regularly return to the same colony, creating the potential for intra- and inter-specific foraging competition in nearby waters. I hypothesised that these demographic groups would exhibit distinct foraging strategies, which reduce competition and facilitate their coexistence. I analysed the diet of adult male, adult female and juvenile NZ fur seals and adult male Australian fur seals and studied the diving behaviour of adult male and lactating female NZ fur seals and the at-sea movements of juvenile, adult male and lactating female NZ fur seals. Female diet reflected that of a generalist predator, influenced by prey availability and their dependant pups� fasting abilities. In contrast, adult male NZ and Australian fur seals used larger and more energy-rich prey, most likely because they could more efficiently access and handle such prey. Juvenile fur seals primarily utilised small lantern fish, which occur south of the shelf break, in pelagic waters. Juveniles undertook the longest foraging trips and adult males conducted more lengthy trips than lactating females, which perform relatively brief trips in order to regularly nurse their pups. Unlike lactating females, some adult males appeared to rest underwater by performing dives that were characterised by a period of passive drifting through the water column. The large body sizes of adult males and lactating females facilitated the use of both benthic and pelagic habitats, but adult males dived deeper and for longer than lactating females, facilitating vertical separation of their foraging habitats. Spatial overlap in foraging habitats among the age/sex groups was minimal, because lactating females typically utilised continental shelf waters and males used deeper water over the shelf break, beyond female foraging grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the regions used by lactating females and adult males. The age and sex groups in this study employed dramatically different strategies to maximise their survival and reproductive success. Their prey and foraging habitats are likely to be shaped by body size differences, which determine their different physiological constraints and metabolic requirements. I suggest that these physiological constraints and the lactation constraints on females are the primary factors that reduce competition, thereby facilitating niche partitioning.

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Bublys, Kasparas. "Diet variability in Eurasian perch (Perca fluviatilis) as a response to environmental variables along a latitudinal gradient." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-365794.

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Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.

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Russell, Vanessa. "Identifying Environmental Factors Driving Differences in Climatic Niche Overlap in Peromyscus Mice." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1565722438217428.

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Raper, Lafferty Diana Jean. "Evolutionary and ecological causes and consequences of trophic niche variation in ursids." Thesis, Mississippi State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3716731.

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Individual variation and fitness are the cornerstones of evolution by natural selection. The trophic niche represents an important source of phenotypic variation on which natural selection can act. Although individual variation is fundamental to species-level ecological and evolutionary change, individual variation is often ignored in population-level approaches to wildlife ecology, conservation and management. Failing to link individual resource use to fitness or to biological outcomes related to fitness limits us to managing for the average resource needs of a population, which may be insufficient for protecting the diversity of resource use within populations and the underlying eco-evolutionary processes that generate that diversity. My goals were to provide insights into the mechanisms that generate and constrain intrapopulation trophic niche variation, evaluate whether linkages exist between individual biological outcomes and variation in food habits across the range of resources consumed within generalist consumer populations and examine how that variation manifests in population-level responses.

I investigated the causes and physiological consequences of intrapopulation trophic niche variation in two generalist consumers, the American black bear (Ursus americanus) and brown bear (U. arctos) across three sites in British Columbia, CAN and at one site in Alaska, USA. My primary tools included stable isotope analysis to estimate diet, enzyme-linked immunoassay of hair to quantify the hormone cortisol for indexing physiological stress, and genetic analyses to identify individuals, species, and sex and to estimate ancestry. I found that individual differences in resource use can result in similar biological outcomes and that similar resource use can result in different biological outcomes. Intra- and interspecific competition, sex-based differences in nutritional and social constraints and annual variation in food availability all influenced trophic niche variation and the resultant biological outcomes. I also found evidence of a link between intrapopulation trophic niche variation and population genetic structure. My results highlight the diverse ecological drivers and diverse consequences of trophic niche variation, which further illuminates why the trophic niche is a nexus for eco-evolutionary dynamics.

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FitzGerald, Alyssa. "Speciation and Ecological Niche Divergence of a Boreal Forest Bird Species Complex." Thesis, State University of New York at Albany, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10276556.

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Evolutionary biologists are supremely interested in the events that cause populations to diverge and speciate, and the mechanisms that maintain divergence over time. Here, I investigate the evolutionary history of a boreal bird species complex. Boreal bird species are co-distributed, diverged during the Pleistocene, and generally have patterns of genetic divergence that are consistent with a single “boreal” clade in northern and eastern North America. The Gray-cheeked Thrush species complex, however, shows a possible species break in eastern North America between the Bicknell’s Thrush ( Catharus bicknelli) and Gray-cheeked Thrush (Catharus minimus ). Using population genetic and genomic analyses of the largest sampling to-date of either species, I find that the eastern break indeed coincides with a species-level divergence, although low levels of admixture in a few individuals and one probable hybrid hint at the possibility of occasional hybridization. Species distribution models (SDMs) of the Last Glacial Maximum revealed that divergence may have been maintained by residence in different late-Pleistocene refugia. However, because speciation occurred mid-Pleistocene, I examined the geographical context of divergence of the Bicknell’s Thrush and Gray-cheeked Thrush using multivariate analyses and ecological niche modeling techniques of local-scale habitat data and broad-scale climate and tree species distributions. Local-scale habitat analyses reveal that the thrushes breed at sites with unique tree species composition, physiognomy (forest structure), and ground cover characteristics; furthermore broad-scale analyses reveal that niche divergence, rather than conservatism, was the predominant pattern for these species, suggesting that ecological divergence has played a role in their speciation. This dissertation supports the hypothesis that the Bicknell’s Thrush and Gray-cheeked Thrush are distinctive species that breed in divergent local- and broad-scale niches and emphasizes that this species-level divergence seems unique among boreal bird species.

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Costa, Rafael Carvalho da 1978. "Mecanismos de coexistência em florestas tropicais = variações ontogenéticas de arquitetura aérea, padrão espacial e performance de espécies congenéricas simpátricas em uma floresta tropical úmida de terras baixas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315019.

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Orientador: Flávio Antonio Maes dos Santos
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A alta diversidade em florestas tropicais tem motivado questionamentos sobre a importância da diferenciação de nicho como mecanismo de coexistência. Nessa hipótese, a heterogeneidade ambiental proporcionaria eixos de diferenciação que facilitariam a coexistência, sendo, portanto, esperadas diferenças entre espécies na associação a gradientes espaciais de recursos e condições. Estudos em pequenas escalas têm encontrado muita variação no percentual de espécies associadas a microambientes, deixando dúvidas sobre a relevância da divergência de nicho como mecanismo de coexistência nessa escala. Neste estudo, avaliamos evidências da importância da divergência de nicho como mecanismo de coexistência investigando padrões de divergência ecológica em dimensões verticais e horizontais, ao longo da ontogenia, de duas espécies arbóreas congenéricas simpátricas em uma floresta tropical úmida. Esse é um sistema útil para este objetivo pois, dada a similaridade ligada a ancestralidade comum, a coexistência seria mais difícil entre essas espécies. Estudamos padrões ao longo do desenvolvimento, utilizando uma classificação de estádios ontogenéticos. Para isso, descrevemos estádios e verificamos o quanto marcadores morfológicos são indicadores adequados de mudanças ontogenéticas de tamanho, sobrevivência, reprodução e crescimento. Para avaliar divergências relacionadas à gradientes verticais de luz, testamos diferenças ontogenéticas de alometria e arquitetura aérea sob a expectativa de que as espécies tivessem morfologias adequadas à sobrevivência na sombra ou ao ganho de altura. Para avaliar divergências em gradientes horizontais, testamos a segregação espacial interespecífica de indivíduos e da mortalidade e crescimento por estádio ontogenético. As espécies apresentaram marcadores morfológicos semelhantes que permitiram identificar os estádios plântula, juvenil e reprodutivo ramificado. Na fase pré-reprodutiva, as características morfológicas sinalizam adequadamente diferenças de tamanho e sobrevivência, mas não crescimento, enquanto a entrada na fase reprodutiva foi melhor indicada pela altura. As trajetórias ontogenéticas dos aspectos demográficos analisados sugerem histórias de vida semelhantes entre espécies. Não encontramos diferenças de alometria e arquitetura aérea conforme as expectativas. Isso ocorreu principalmente por semelhanças ontogenéticas nas dimensões de troncos e copa. No entanto, houve diferenças na forma como as espécies preenchem suas copas, enquanto uma espécie tem copas muito ramificadas com folhas menores, a outra tem copas pouco ramificadas com folhas maiores. Estudos posteriores são necessários para verificar se essas diferenças conferem vantagem diferencial, contribuindo para a coexistência. As expectativas de segregação espacial interespecífica só foram confirmadas em estádios iniciais. Porém, não foi possível excluir a influência da dispersão no estabelecimento desses padrões. Raramente houve segregação espacial interespecífica nos estádios posteriores e não houve evidência de melhor desempenho em microhabitats preferenciais. Ao contrário, as localidades propícias ao crescimento foram comumente semelhantes. A grande variabilidade dos padrões interespecíficos entre estádios e localidades, e a aderência a modelos nulos de sobrevivência e mudança de estádios espacialmente aleatórios sugerem que as relações espaciais interespecíficas são dependentes de eventos estocásticos (tempo e espaço), sendo a mortalidade e crescimento correntes aparentemente incapazes de alterar padrões espaciais pré-existentes na escala temporal estudada. Neste estudo, as expectativas de divergências ecológicas entre espécies não foram corroboradas. Os resultados apontam para a possibilidade de que a diferenciação de nicho não seja essencial para a coexistência de espécies arbóreas em florestas tropicais
Abstract: High biodiversity in tropical forests has motivated an extensive debate on the importance of niche divergence as a coexistence mechanism. According to this hypothesis, coexistence would be promoted by specialization to portions of niche axis and, therefore, spatial associations of species in gradients of resources and conditions are expected. The spatial evidence for niche divergence is doubtful, because small scale studies have been finding large differences in the percentage of species associated with microhabitats. In this study, we aimed to search for evidences of niche divergence as a coexistence mechanism by investigating ecological divergence related to vertical and horizontal dimensions between a pair of sympatric congeneric tree species in a wet tropical forest. Congeneric species are useful for our objectives because due to common heritage, coexistence should be more difficult for such species. Because we chose to study a broad developmental coverage, we adopted an ontogenetic stage classification. To utilize this approach, we described stages and verified the suitability of morphological markers as indicators of size and performance transitions. Divergence related to vertical light gradients was assessed by tests of aboveground alometric and architectural differences under the expectation of morphological differences related to either survival in shade or rapid height gain. Divergence in horizontal gradients was assessed by tests of interspecific spatial segregation (ISS) of individuals and performance in ontogentic stages. We found similar morphological markers between species that enabled us to recognize seedling, juvenile, and branched reproductive stages. Morphological markers were able to indicate size and performance (except for growth) transitions at vegetative phase, but they were not efficient in indicating the onset of reproduction, of which size was a better indicator. Similarities in ontogenetic trajectories of size and performance suggests life history coincidence between species. Our expectations on allometry and architecture were not met, mainly because both species had similarly constructed crowns and trunks throughout ontogeny. However, we found differences among species in the mode of crown filling. One species had small leafed, intensely ramified crowns, whereas the other seemed to compensate for low branching levels by having large leaves. Future studies are needed to verify whether this can be related to a differential advantage contributing to coexistence. The expected ISS was only common in early stages, but we were not able to exclude the possibility of dispersal driven patterns. In later stages, we rarely found ISS, and there was no evidence of better performance of either species in preferred microhabitats. Otherwise, we found that suitable sites for growth often coincided. High variability of interspecific spatial patterns among stages and sites and adherence to null models of spatially random survival and transition to other stages suggests that spatial relationships between species are mainly due to stochastic events (space, time) and that current mortality and growth are not able to change preceding spatial patterns during the studied timescale. In summary, the general expectations of ecological divergence between species were not met. Our results point to the possibility that niche divergence should not be an essential requisite for tree species coexistence in tropical forests
Doutorado
Biologia Vegetal
Doutor em Biologia Vegetal

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Sokol, Eric Robert. "Community ecology of aquatic insects in forested headwater streams in the southern Appalachians." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29110.

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Competing paradigms of community assembly emphasize different mechanisms for predicting patterns in biogeography. Niche assembly emphasizes the role of environmental gradients as filters that organize a metacommunity by locally selecting colonizers with similar functional traits, whereas dispersal assembly emphasizes the importance of source pool characteristics and dispersal limitation in organizing a metacommunity. In this study, I developed a framework that uses spatially explicit patterns in taxonomic and functional measures of community composition as diagnostics for community assembly processes for benthic macroinvertebrates in headwater streams in the southern Appalachians. Distance decay in taxonomic and functional similarity was used to determine the scales at which taxonomic turnover occurred within functional niches. Trait-neutral models of community composition were used as null models to assess which functional traits were the best candidates to explain how community composition was influenced by environmental gradients: an assessment of niche-based community assembly. Regional scale patterns suggested that niche-based community assembly was the dominant mechanism organizing community composition in headwater streams at local scales (<30km). Therefore, I compared how well trait-neutral models identified functional traits as relevant to community sorting against how well observed trait distributions correlated with environmental variation at a local scale, in the Ray Branch catchment (<10km study extent). Functional traits exhibiting non-random distributions within the Ray Branch watershed were most strongly correlated with environmental variation. Lastly, I assessed how the influences of niche and dispersal assembly on benthic macroinvertebrate community composition were affected by disturbance (shelterwood logging). Environmental variables defining the habitat template, and macroinvertebrate community composition, were measured before and after the disturbance; and path analysis was used to quantify the disturbance effect. The relationship between environmental variation and functional composition increased following logging, indicating disturbance augmented the influence of environmental filters, and consequently, the importance of niche-based community assembly. My dissertation provides the framework for a novel assessment of taxonomic and functional community composition data to infer the types of ecological dynamics that organize communities in the landscape. Additionally, this work provides a theoretical basis for assessing how dominant ecological processes change, in predictable ways, in response to changes in the habitat template.
Ph. D.

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Dobos, Jean A. "A social ecology study of media competition and managerial gratifications from business news /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266011221537.

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Doniol-Valcroze, Thomas. "Habitat selection and niche characteristics of rorqual whales in the northern Gulf of St. Lawrence (Canada)." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18774.

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Habitat selection influences the distribution patterns of animals and how they partition their ecological niches. However, studies of habitat selection seldom model temporal variability and focus primarily on terrestrial ecosystems where habitat patches change over comparatively long time scales. In marine ecosystems, ignoring the time-varying characteristics of habitats might lead to a poor understanding of ecological relationships. Blue (Balaenoptera musculus), finback (B. physalus), humpback (Megaptera novaeangliae) and minke (B. acutorostrata) whales occur in sympatry in the Gulf of St. Lawrence (Canada) during the feeding season. I combined boat surveys with remote-sensing technology and computer ocean models to study habitat selection and niche characteristics of these rorqual whales for the years 1997-2002. All four species responded to the temporal variability of their environment by selecting a combination of time-varying and static factors that differed from the available habitat and were likely linked with prey availability, namely shallow banks, steep seabed slope, cold and saline surface waters, deep and cold intermediate layer. Moreover, distribution of whale sightings was highly correlated with thermal fronts, a dynamic meso-scale process that increases biological productivity and aggregates prey. Spatial distribution differed among species, likely reflecting differences in feeding strategies that could have evolved to alleviate inter-specific competition. There was clear spatial partitioning of the habitat use between species, and some separation in time. Fine-scale selection of dynamic variables appears to be the main mechanism facilitating co-occurrence. Minke whales had a specialised niche centred on shallow coastal waters. Deeper offshore waters and a colder intermediate layer characterised the niches of finback and humpback whales. The endangered blue whale had the narrowest niche, characterised by high salinity cold surface temperature and s
La sélection de l'habitat influence la distribution des animaux et la manière dont ils coexistent. Cependant, les études prennent rarement en compte la variabilité temporelle et se penchent surtout sur les écosystèmes terrestres où les caractéristiques évoluent sur des échelles de temps relativement longues. Dans les écosystèmes marins en revanche, ignorer le caractère dynamique de l'habitat peut conduire à une mauvaise compréhension des relations écologiques. Des rorquals bleus (Balaenoptera musculus), communs (B. physalus), à bosse (Megaptera novaeangliae) et des petits rorquals (B. acutorostrata) se rencontrent en situation de sympatrie dans le golfe du Saint-Laurent (Canada) durant leur saison d'alimentation. J'ai combiné des relevés en bateau avec des technologies d'échantillonnage à distance et des modèles informatiques du Saint-Laurent pour étudier la sélection de l'habitat et les niches écologiques de ces rorquals entre les années 1997 et 2002. Dans ma zone d'étude, les quatre espèces répondaient à la variabilité temporelle de leur environnement en sélectionnant une combinaison de facteurs dynamiques et statiques qui différaient de l'habitat disponible et étaient liés à la disponibilité de leurs proies : bancs peu profonds, topographie sous-marine pentue, eaux de surface froides et salées, couche intermédiaire plus froide et plus profonde. De plus, la distribution des observations de baleines était hautement corrélée avec les fronts thermiques, un processus dynamique qui augmente la productivité biologique et regroupe les proies. Les schémas de distribution spatiale différaient entre les espèces, reflétant probablement des différences de stratégie alimentaire apparues afin d'alléger la compétition interspécifique. Les quatre espèces semblaient se partager l'habitat dans l'espace et dans le temps, principalement au moyen d'une sélection à petite échelle des variables dynamiques. Les petits rorquals av

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26

Brum, Mauro 1984. "Partição de recursos hídricos em comunidades vegetais de campo rupestre e campo de altitude no Sudeste brasileiro." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316211.

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Orientador: Rafael Silva Oliveira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia.
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Resumo: A partição de recursos hídricos do solo é um dos modelos plausíveis para explicar os mecanismos que promovem a coexistência e a diferenciação de nicho entre espécies em comunidades vegetais. As raízes constituem a principal interface de troca de água entre a planta e o solo, de modo que profundidade radicular é um atributo chave que pode influenciar o funcionamento hidráulico das plantas. O campo rupestre e o campo de altitude são vegetações campestres que ocorrem em montanhas ou chapadas sob diferentes regimes de água devido às diferenças climáticas e pedológicas, sendo o campo rupestre mais árido que o campo de altitude. Essas comunidades são bem conhecidas devido à alta diversidade de espécies, mas pouco se sabe a respeito da diversidade de estratégias de uso de água. Entender as estratégias hidráulicas das plantas é importante para fazer previsões das respostas das comunidades em relação às mudanças climáticas. Diante disso, o nosso objetivo foi responder: quais são os padrões de aquisição e uso de água por plantas que coexistem em uma vegetação de campo rupestre e outra de campo de altitude? Além disso, quais são as estratégias de uso de água entre as plantas com sistemas subterrâneos contrastantes nessas comunidades? Nós avaliamos a composição de isótopos estáveis da água do solo e contrastamos com a composição isotópica da água do xilema de 15 espécies de plantas em cada comunidade. A composição isotópica da água do xilema foi usada como um indicador para estimar a profundidade do solo na qual as plantas estão absorvendo a água. Também fizemos escavações das raízes para verificar qual é o tipo morfológico de cada espécie e contrastar com os resultados da composição isotópica da água do xilema. Além disso, medimos o potencial hídrico da madrugada, do meio dia e a condutância estomática máxima três vezes durante a estação seca (junho, julho e agosto). Nós demonstramos que em ambas as comunidades há uma diversidade interespecífica de formas de sistemas subterrâneos, sendo que o campo rupestre apresentou maior variação interespecífica de uso de água em perfis verticais do solo. As plantas do campo de altitude apresentam raízes mais superficiais do que no campo rupestre. Além disso, demonstramos que a profundidade do sistema radicular é um bom preditor do potencial hídrico da madrugada e do grau de regulação estomática para as plantas do campo rupestre, mas não do campo de altitude. Não encontramos relação entre a profundidade do sistema radicular e o potencial hídrico do meio dia em ambas as comunidades
Abstract: Soil water partitioning is a plausible model to explain the mechanisms that allow species coexistence and niche segregation in plant communities. Roots are the main interface of water exchange between plant and soil, so rooting depth is a key trait that affects whole-plant hydraulic function. The campos rupestres and campos de altitude are two shrubland communities that occur in mountainous plateaus under contrasting water regimes due to differences in their climatic and pedological variables, campos rupestres being more arid than campos de altitude. These communities are well known for their high species diversity but little is known about the diversity of water use strategies. Understanding plant hydraulic strategies is important for improving predictions of community responses to changes in climate. Our goal was to respond: what are the patterns of water acquisition and use in campo rupestres and campo de altitude? Furthermore, what are the water use strategies of plants with contrasting rooting depths in these plants communities? We evaluated the ?D of soil water and xylem water of 15 species in each community. The ?D of xylem water was used as proxy of rooting depth. We also excavated the roots of all species to evaluate their root morphological pattern and to compare with the isotopic data. Furthermore, we measured pre-dawn and midday water potentials and stomatal conductance three times during the dry season (June, July and August, 2012). We found a high interespecific diversity of root types in both communities and higher variance of hydraulic traits at campo rupestre. Campo de altitude plants had shallower roots than campo rupestre. Moreover, we demonstrated that pre-dawn water potential is a good predictor of rooting depth, which in turn is a good predictor of the degree of stomatal control for campo rupestre community but these patterns were not found at campo de altitude. We did not find any relationship between rooting depth and midday water potential for both communities
Mestrado
Ecologia
Mestre em Ecologia

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27

Crail, Todd D. "The Ecological Niche of Darters (Pisces:Percidae) Across Multiple Scales in the Ohio River Basin." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344985634.

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Moen, Daniel S., and John J. Wiens. "Microhabitat and Climatic Niche Change Explain Patterns of Diversification among Frog Families." UNIV CHICAGO PRESS, 2017. http://hdl.handle.net/10150/624675.

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A major goal of ecology and evolutionary biology is to explain patterns of species richness among clades. Differences in rates of net diversification (speciation minus extinction over time) may often explain these patterns, but the factors that drive variation in diversification rates remain uncertain. Three important candidates are climatic niche position (e.g., whether clades are primarily temperate or tropical), rates of climatic niche change among species within clades, and microhabitat (e.g., aquatic, terrestrial, arboreal). The first two factors have been tested separately in several studies, but the relative importance of all three is largely unknown. Here we explore the correlates of diversification among families of frogs, which collectively represent approximate to 88% of amphibian species. We assemble and analyze data on phylogeny, climate, and microhabitat for thousands of species. We find that the best-fitting phylogenetic multiple regression model includes all three types of variables: microhabitat, rates of climatic niche change, and climatic niche position. This model explains 67% of the variation in diversification rates among frog families, with arboreal microhabitat explaining approximate to 31%, niche rates approximate to 25%, and climatic niche position approximate to 11%. Surprisingly, we show that microhabitat can have a much stronger influence on diversification than climatic niche position or rates of climatic niche change.

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Gimonneau, Geoffrey. "Bio-écologie de la spéciation : partage de la niche écologique chez deux espèces naissantes d'anophèles au Burkina Faso." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20118.

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En Afrique de l'Ouest, le moustique An. gambiae s.s vecteur majeur du paludisme est subdivisé en deux formes moléculaires, M et S, génétiquement et écologiquement différenciées. La forme moléculaire M se développe préférentiellement dans des collections d'eau pérennes en zone aride, généralement d'origine anthropique, permettant sa présence tout au long de l'année alors que la forme S se reproduit principalement dans des gîtes temporaires de savane humide dépendant des précipitations et disparaît en saison sèche. Cette subdivision génère des profils de dynamique de transmission palustre différents en fonction des zones où ces formes sont implantées. Dans ce contexte, cette thèse a pour objectif l'étude des facteurs écologiques de différenciation entre M et S, en se focalisant notamment sur leur écologie larvaire, afin de mieux appréhender leur distribution actuelle et future. L'étude de la distribution des populations naturelles de ces vecteurs dans une zone d'endémie palustre au Burkina Faso a permis de mettre en évidence que les niches écologiques de ces deux formes sont en étroite corrélation avec la temporalité des milieux aquatiques et la complexité des écosystèmes qu'ils hébergent. La forme M apparaît clairement liée aux habitats permanents anthropiques et à la structure des communautés qu'ils soutiennent alors que la forme S ainsi que l'espèce jumelle An. arabiensis sont associées aux habitats simples et temporaires, majoritairement retrouvés en zone rurale de savane.Cette distribution des deux formes le long d'un gradient d'hydropériode est en accord avec les interactions dominantes et les adaptations qu'elles induisent afin de pouvoir exploiter ces milieux. La forme S, associée aux milieux temporaires, s'est révélée plus compétitive que la forme M en diminuant son temps de développement larvaire en présence de compétiteurs (forme M). L'étude de la pression de sélection due à la prédation, interaction dominante dans les milieux permanents, démontre que la forme M est moins susceptible que la forme S. L'analyse du comportement larvaire a permis de mettre en évidence des différences entre ces deux formes, notamment l'existence d'un comportement plus plastique chez la forme M qui réduit son activité en présence d'un prédateur. Ce mécanisme est une des adaptations qui a favorisé le succès d'An.gambiae dans les milieux permanents.Notre approche, basée sur l'écologie larvaire des formes M et S d'An. gambiae nous a permis de mieux comprendre les processus par lesquels ces vecteurs ont évolué et se sont adaptés à différents contextes écologiques. Ces adaptations reflètent la spécialisation de ces deux formes dans leur milieu respectif et permettent en partie d'expliquer la ségrégation écologique observée sur le terrain. L'amélioration de nos connaissance sur la bio-écologie de ces vecteurs est primordiale afin d'en apprécier le potentiel évolutif dans le contexte actuel des changements globaux
In West Africa, the main Malaria vector, the mosquito Anopheles gambiae is actually subdivided into two molecular forms named M and S, which can be genetically and environmentally differentiated. The M form preferentially breeds in permanent freshwater collections mainly resulting from human activity and is reproductively active all year round, whereas the S form thrives in temporary breeding sites and is present during the rainy season only. This subdivision generates different dynamics of Malaria transmission in areas where these forms are found. In this context, this thesis aims to study the ecological factors of differentiation between M and S, focusing on their larval ecology to better understand their current and future distribution.The study of the distribution of natural populations of these vectors in an endemic area in Burkina Faso has provided evidence that the ecological niches of these forms are closely correlated with the degree of temporality and the community complexity of aquatic ecosystems. The M form is clearly linked to permanent anthropogenic habitats and the structures they support, while the S form and its sibling species An. arabiensis are associated with simple and temporary habitats, mostly found in rural savannas.The distribution of the two forms along a hydroperiod gradient is consistent with the dominant interactions and adaptations they induce in order to be able to exploit their environments. In relation to temporary habitat, the S form was more competitive than the M form by reducing its larval development time in the presence of competitor (M form). The study of selection pressure due to predation, dominant interaction in permanent habitat, shows that the M forms suffer lesser predation rate than the S form. Analysis of larval behavior highlighted differences between these two forms, such as the existence of a more plastic behavior in the form M, which reduced its rate of activity in predator presence. This mechanism is one of the adaptations that have facilitated the success of An. gambiae in permanent aquatic habitats.Our approach, based on the larval ecology of M and S forms of An. gambiae has enabled us to better understand the processes by which these vectors have evolved and adapted to different ecological contexts. These adaptations reflect the specialization of these two forms in their respective habitats and can partially explain the ecological segregation observed in the field. Improving our knowledge on bio-ecology of these vectors is essential to appreciate their evolutionary potential in the current context of global change

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Radegård, Madeleine. "Habitatanvändning av svartmes (Periparus ater) och entita (Poecile palustris)." Thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-65418.

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Competition is common between closely related species, no less between birds. For tits in temperate forests, competition for food and space is usually stronger during winter, as foraging opportunities are few. Many species with an otherwise broad diet, therefore, start eating the same available food items and thus increase their overlap in the use of food resources. The purpose of this study was to investigate whether coal tits and marsh tits compete with each other. The observations were made in 10 selected locations with varying types of forests. In the study, 20 entrants and 20 blacks were observed for 5 minutes per individual. Every minute the position of the individual was noted in the tree.The results indicate an asymmetrical competition between the species because marsh tits changed its habitat use and were found lower in trees in the presence of coal tits, whereas coal tits did not change its habitat use in the presence of marsh tits. The movement by the Marsh tits can then reduce competition and give both species a better chance of living together.
Konkurrens är vanligt mellan närbesläktade arter, inte minst mellan fåglar. Konkurrensen om mat och boplatser blir oftast starkare på vinterhalvåret då det är svårare att hitta mat och många arter som annars föredrar olika sorters föda då börjar äta samma sort. Syftet med denna studie var att undersöka om svartmes och entita konkurrerar med varandra. Observationerna gjordes på 10 utvalda platser med varierande skogstyper. I studien observerades 20 entitor och 20 svartmesar i 5 minuter per individ. Varje minut noterades individens position i trädet. Resultaten visar att det kan förekomma en asymmetrisk konkurrens mellan arterna då entitan flyttade sig nedåt i höjdnivå i närvaro av svartmes, medan svartmes inte ändrade plats i närvaro av entita. Entitans nedflyttning kan då minska konkurrensen och ge båda arter bättre möjlighet till samlevnad.

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Farquhar, Michael Robert. "Interspecific interactions of the sea urchin Parechinus angulosus and the effect of variations in microhabitat availability." Thesis, Rhodes University, 1995. http://hdl.handle.net/10962/d1005406.

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Intertidal populations of the sea urchin Parechinus angulosus were examined at seven sites along the south and east coasts of South Africa. At the five southerly sites, P. angulosus occurred in allopatry, while, at the two northerly sites, it occurred in sympatry with several species of Indopacific sea urchins. At the five southerly sites, there was a significant correlation of number of sea urchins per pool with the surface area of the overhang in that pool. This relationship broke down for P. angulosus at the two northerly sites, where there was a significant correlation between these two factors for Stomopneustes variolaris. The density of populations of P. angulosus at the two northerly sites, although not significantly different from all five southerly sites, were considerably lower. There was a significant difference between the mean size of populations at the seven sites. Although no direct evidence is available, a competitive interaction between these two species is proposed to explain the observed patterns of microhabitat utilization and densities. Two series of manipulative experiments were conducted at Kowie Point, where P. angulosus occurs in sympatry, The first, involved urchin removals from three experimental sites. The percentage cover of four functional algal groups was monitored in three experimental and three unaltered control sites over a three month period in spring (Sept. - Dec.) 1993. Two 100 point 0,25m² random point quadrats were thrown at each of the six sites at approximately monthly intervals over the experimental period. Since initial cover of algae varied at the six sites, ANOVA's of the change in percentage cover of four functional algal groups were used to determine treatment effects. No treatment effects were identified for any of the four functional algal groups. There was a strong negative correlation between the percentage cover of foliose algae and encrusting coralline algae, suggesting the possibility of a competitive relationship between them. The second, involved the experimental manipulation of microhabitat availability. The blocking of overhangs, by means of cement filled bags, resulted in an approximate 50% decrease in the total number of urchins in the two experimental pools, and the two control pools without overhangs. However, in the control pool with overhangs there was a slight increase in the number of urchins over the same period. Clearly, the presence of suitable shelters, is a prerequisite for the maintenance of dense intertidal population of P. angulosus. It is proposed that, due to the exposed nature of the South African coast, intertidal populations of P.angulosus are restricted to inhabiting suitable shelters from which they emerge to feed on passing drift algae. The implications of these findings are discussed in terms of current ecological literature.

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32

Yadav, Sunita. "The Influence of Climate and Topography in Modeling Distributions for Species with Restricted Ranges: A Case Study Using the Hawaiian Endemic Plant Genus, Schiedea (Caryophyllaceae)." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690823.

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33

Nichols, Rebecca Jo. "Biodiversity of aquatic insects in relation to temperate and tropical land use, and the life histories and microhabitat associations of Lotic mayflies /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9737899.

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Colombo, Alexandre Falanga. "Consequencias potenciais das mudanças climaticas globais para especies arboreas da Mata Atlantica." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315801.

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Orientador: Carlos Alfredo Joly
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Desde o início da colonização portuguesa, a Mata Atlântica, um dos dez biomas mais ricos e diversos do mundo, sofreu uma redução considerável em extensão e diversidade. O extrativismo, o avanço da agricultura extensiva e o rápido crescimento das cidades na faixa litorânea do país, foram e continuam sendo em algumas regiões, responsáveis pela redução da vegetação nativa. Dados recentes mostram que restam apenas 7% da cobertura florestal original, e menos do que 5% são efetivamente de florestas nativas pouco antropizadas. Esta situação pode estar sendo agravada devido às mudanças nos padrões climáticos terrestres. Exarcebados pela ação humana, o aquecimento global, a mudança do regime de chuvas, entre outras alterações atmosféricas, podem modificar substancialmente o padrão de distribuição das espécies arbóreas dos biomas nativos. Este processo pode resultar na diminuição da área de ocorrência ou mesmo na extinção de espécies. Este trabalho tem como objetivo, através de técnicas de modelagem preditiva, delinear áreas de distribuição geográfica futura de 38 espécies arbóreas típicas da Mata Atlântica lato sensu, considerando dois cenários de aquecimento global nos próximos 50 anos. No cenário otimista, que prevê um aumento anual de 0,5% na concentração de CO2 da atmosfera, o aumento médio da temperatura terrestre seria = 2 oC; já no cenário pessimista, com um aumento médio de 1% na concentração de CO2 atmosférico, o aumento médio da temperatura seria da ordem de 4 oC. Considerando estes parâmetros, e usando GARP-Genetic Algorithm for Rule-set Prediction, foram gerados três modelos para cada espécie: um de distribuição presente e dois de cenários futuros, um otimista e outro pessimista em relação às emissões de CO2 até 2050. Os resultados obtidos mostram, de forma alarmante, uma redução na área de ocorrência potencial das espécies estudadas, além de um possível deslocamento destas para regiões mais ao sul do que as atualmente observadas. Em média, no cenário otimista, a redução na área de ocorrência potencial é de 25%, e no cenário pessimista de 50%. Espécies como Euterpe edulis, Jacaranda puberula, Mollinedia schottiana, Virola bicuhyba, Inga sessilis, Ecclinusa ramiflora e Vochysia magnifica são as que poderão sofrer mais os efeitos do aumento da temperatura global. A geração de informação sobre as conseqüências das atividades humanas na terra vem aumentando, fornecendo subsídios técnicos para a tomada de decisões no âmbito político, econômico e acadêmico. Apesar de, no estágio atual, as ferramentas de modelagem não terem a precisão desejada, a consistência dos padrões de deslocamento e redução na área potencial de ocorrência reforçam a importância delas serem incorporadas à formulação e aperfeiçoamento das políticas de conservação de nossos ecossistemas nativos
Abstract: One of the top ten most diverse rich forests in the word, the Brazilian Atlantic Forest has been suffering significant losses since the Portuguese arrived in Brazil in 1500. Wood, palm hart and epiphytes extraction, extensive agriculture and the expansion of large cities still are the main threats. Recent data shows that there are less then 7% of native forest left, and from those only 5% can be considered pristine. Aggravated by human activities global warming, changes in rainfall patterns, among other changes may affect substantially native trees geographical distribution. The result of this process may be a reduction in the area of occurrence of species and, ultimately, in the extinction of a large number of them. In this study we used predictive modeling techniques to determine present and future geographical distribution of 38 species of tree that are typical of the Brazilian Atlantic Forest (Mata Atlântica lato sensu), considering two global warming scenarios. The optimistic scenario, based in a 0,5% increase in the concentration of CO2 in the atmosphere, predicts an increase of up to 2 oC in Earth¿s average temperature; in the pessimistic scenarios, based in a 1% increase in the concentration of CO2 in the atmosphere, temperature increase may reach 4 oC. Using these parameters and the Genetic Algorithm for Ruse-set Predictions/GARP three models were produced: one with the present distribution of the species based in occurrence points registered in literature, the other two were based in changes of Earth¿s mean temperature by 2050 using the optimistic and the pessimistic scenarios of CO2 emission. The results obtained show an alarming reduction in the area of possible occurrence of the species studied, as well as a shift towards the most southern part of Brazil. In average, using the optimistic scenario this reduction is of 25% while in the pessimistic scenario it reaches 50%. Among the species studied Euterpe edulis, Jacaranda puberula, Mollinedia schottiana, Virola bicuhyba, Inga sessilis, Ecclinusa ramiflora e Vochysia magnífica are the ones that will suffer the worst reduction in their possible area of occurrence. Nowadays scientific certainty about climate changes as a consequence of human activities is so strong, that it must be taken in account by all spheres of action: political, economic and academic. Although predictive models are not yet as precise as we would like and need, the consistency of patterns of shifts and reductions in areas of potential occurrence of tropical plant species strengthen the importance of incorporating them in planning and implementing native biodiversity policies
Mestrado
Ecologia
Mestre em Ecologia

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35

Murphy, Melanie April. "New approaches in landscape genetics and niche modeling for understanding limits to anuran distributions." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Dissertations/Summer2008/m_murphy_071708.pdf.

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36

French, Elizabeth A. "Investigation of Factors Influencing Niche Differentiation of Ammonia-oxidizing Archaea and Bacteria in Freshwater Environments." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1366113455.

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37

Driscoll, William Wallace. "Social and Asocial Niche Construction in Microbial Populations." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228457.

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Cooperation presents a major challenge for evolutionary theory: how can competition favor a trait that imposes a cost on the individual expressing it while benefitting another? This challenge has been answered by theory that emphasizes the importance of assortment between individuals that tend to cooperate and those who tend to behave selfishly, or `cheat'. Microbial cooperation remains puzzling, given the generally high genetic and taxonomic diversity of most microbial communities. Many microbial populations rely on shared, beneficial extracellular products for an array of functions in nature. However, when these lineages are maintained in liquid cultures, many are invaded and outcompeted by spontaneous `cheater' mutants that forego investments in these products while benefitting from those produced by neighbors. The apparent evolutionary instability of microbial investments in extracellular products in well-mixed laboratory cultures finds a natural parallel in the phenomenon of toxic microalgal blooms. These extremely dense populations of often free-living microalgae destroy populations of competing microalgae and grazing zooplankton that normally control population densities. Bloom populations of planktonic microalgae are unstructured, and seem ill suited for the evolution of cooperation. In this thesis, I have established a new theoretical framework for understanding the evolution of microbial external goods. This framework highlights the importance of cell-level structure in the distribution of these external products, as well as genetic structuring in populations. This perspective informed an investigation into the social niche of a biofilm-dwelling regulatory mutant of the important biocontrol strain Pseudomonas chlororaphis. In the highly self-structured environment of a bacterial biofilm, a surprising mutualistic association between this mutant and the wild type emerged, underscoring the importance of microbial ecology in understanding the evolution of niche construction. Extending these lessons to the evolutionary problem of exotoxins in free-swimming microalgae yields the novel possibility that fluctuations in density of toxic strains shift a cell-level functioning exotoxin into a true public good that may be exploited by cheaters. I show that exotoxicity can serve cell-level functions in Prymnesium parvum. Despite these cell-level benefits, the existence of nontoxic lineages within toxic blooms hints at a complex interaction between rapid evolutionary and ecological changes in toxic blooms.

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Lu, Ruey-Pyng. "Multivariate nichemetrics." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74739.

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In the study of ecological community structure, the multivariate niche model has always been the assumed structural model. This model is closely connected to the multivariate two-sample problem. Important to the understanding of species interactions in a community is the measurement of the degree to which the niches of two species overlap, or to measure the similarity between the resource use distributions of the species. Discriminant analysis is the tool used most often to analyze the similarity. In this study, we discuss the most commonly used similarity measures, and develop measures that are less dependent on the assumptions of the usual discriminant analysis. Specifically measures arc derived assuming normal distributions with heterogeneous variance-covariance matrices arc derived. The problem of estimating the measures and their precision and accuracy is investigated. Two methods, the jackknife and the bootstrap, arc described for estimating the bias and variance of an estimated measure. The performance of these methods was evaluated using simulation. When the number of variables involved in the model is large, the estimates of these measures may be severely biased, and the bias is consistently negative. By collecting larger samples the bias can be reasonably adjusted. Two potentially important factors affecting results arc the disparity in the means and the heterogeneity of the variance-covariance matrices. It is shown that when the mean separation is small, the heterogeneity of the covariance matrices has a moderate effect on the bias, but the effect is diminished when the mean separation becomes larger. The variance of the similarity estimates is also related to the value of the measure and is a quadratic function of the similarity. The logarithmic transformation of the similarity is seen to linearize the variance of the similarity estimate. The jackknife method gives good adjustment of the bias of the estimated measures. Generally, the bootstrap method performs worse than the jackknife method. In some cases, especially when there are many redundant variables neither method gives reliable results.
Ph. D.

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39

Ward, Michelle V. "Niches and Nosey Neighbors: Exploring How Community Dynamics and Habitat Characteristics Impact Reproductive Success in Forest Interior Bird Communities." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1534947799512093.

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Swisher, Robert E. "Paleobiogeographical and evolutionary analysis of Late Ordovician, C₅ sequence brachiopod species, with special reference to Rhynchonellid taxa." Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1245445583.

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Roark, Selena S. "Ecological Niche Modeling of the North American Giant Salamander: Predicting Current and Future Potential Distributions and Examining Environmental Influences." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3072.

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North American Giant Salamanders (Cryptobranchus alleganiensis), commonly known as hellbenders, have been experiencing a population decline for decades due to human influences, such as pollution and habitat destruction. Many efforts are underway to save the hellbender but their entire potential geographical range has not been well-studied. Currently, hellbender populations are delineated by county boundaries and are on the International Union for Conservation of Nature Red List. The Genetic Algorithm for Rule-set Production, an Ecological Niche Model, was used to model the current hellbender potential distribution at a macro-scale under two different environmental scenarios. Additionally, future potential distributions were projected under two different climate change scenarios (Representative Concentration Pathways) to predict where possible habitat loss and expansion may occur in coming decades. Niche modeling was also used to evaluate the influence of environmental parameters across geography and between two sub-species of hellbender, the Eastern hellbender and the Ozark hellbender. Results showed that vegetation indices had some influence on current distribution predictions, while future models revealed that potentially large areas of currently suitable habitat may be lost, especially in the Ozark Mountains and the Southern Appalachian Mountains. Habitat expansion was predicted for several areas in the New England region of the northern Appalachian Mountains. The most influential variables were the maximum temperature of the warmest month, temperature annual range, and annual precipitation, while slope and elevation were less influential. However, areas of very high slope and elevation were not suitable for hellbenders, confirming previous descriptive habitat analyses. Current and future modeled distributions will provide conservationists with a more specific, and quantified, geographical and ecological description of where environmentally suitable areas exist for hellbenders. Micro-scale, stream-based studies provide areas of future research.

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Farallo, Vincent R. "Notes from the Underground: Linking Microhabitat and Species Distributions of Plethodontid Salamanders." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou148156741016879.

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Lehtonen, Emily. "The Behavioural Ecology of a Potentially Undescribed Morph of Saki Monkey (genus Pithecia) in a Highly Diverse Primate Community." Thesis, Uppsala universitet, Institutionen för ekologi och genetik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-314977.

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The importance of tropical forests for global diversity and ecosystem function is well established in scientific literature, but is undermined by gaps in our knowledge of tropical ecosystems and species. Primates play important functional roles in these ecosystems, and despite constituting one of the most well-recognised taxa in the world, many species remain poorly studied. The Area de Conservación Regional Communal Tamshiyacu-Tahuayo (ACRCTT), located in the northeastern Peruvian Amazon, harbours one of the most diverse primate assemblages in the world and presents an ideal opportunity for the study of primate communities and mechanisms of their coexistence. Previous research has recorded the presence of an atypically coloured morph of monk saki monkeys (Pithecia monachus, sensu Marsh 2014) living in sympatry with a population of burnished sakis (Pithecia inusta, sensu Marsh 2014) in the reserve. In this study, the behavioural ecology of this potentially undescribed morph of saki monkey is described, using continuous focal data collected during the early wet season in the ACRCTT. The sakis were most often encountered in multi-adult groups and in the upper forest strata. The observed feeding strategies suggest that fruits and/or seeds constitute the sakis' primary food source in the wet season, although arthropods were also ingested during a large proportion of feeding records. Sex differences in behavioural patterns provide support for a difference in male and female investment in group defence. As only the monk saki morph was encountered during the study, the potential for seasonal habitat differentiation between the saki populations at the ACRCTT is discussed. A survey of primates in flooded and non-flooded forest areas at the ACRCTT was also conducted, in which nine of the 14 primate species recorded at the ACRCTT were encountered. Significant differences in the vertical distribution of primate groups provide evidence for vertical stratification in the ACRCTT primate community. This study contributes to previous research on the poorly-studied Pithecia genus, and provides insights into the mechanisms of niche differentiation between Pithecia and other primates.

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Mittanck, Cody M. "Exploring A Stable Aspen Niche Within Aspen-Conifer Forests of Utah." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1241.

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Quaking aspen (Populus tremuloides Michx.) is the most widespread broadleaf tree species of North America. Increasing evidence shows that aspen has diverging ecological roles across its range as both “seral” and “stable” aspen community types. This leads us to believe that the successional pathway of aspen may not always lead to a climax conifer sere, but may in some cases consist of persisting stands of pure aspen. This study is an attempt to understand the relationship of aspen community types to climatic, physical, and biophysical variables by modeling patterns of aspen and conifer distribution using remote sensing and GIS technology. Study methodologies and results were specifically designed to aid land managers in identifying extent and status of aspen populations as well as prioritizing aspen restoration projects. Four study sites were chosen in order to capture the geographic and climatic range of aspen. Photointerpretation of NAIP color infrared imagery and linear unmixing of Landsat Thematic Mapper imagery were used to classify dominant forest cover. A Kappa analysis indicates photointerpretation methods to be more accurate (Khat=92.07%, N=85) than linear unmixing (Khat=51.05%, N=85). At each plot, variables were calculated and derived from DAYMET data, digital elevation models, and soil surveys, then assessed for precision and ability to model aspen and conifer distributions. A generalized linear model and discriminant analysis were used to assess habitat overlap between aspen and conifer and to predict areas where “stable” aspen communities are likely to occur. Results do not provide definitive evidence for a “stable” aspen niche. However, the model indicates 60 to 90 cm of total annual precipitation and topographic positions receiving greater than 4,500 Wh m‐2 d‐1 of solar radiation have a higher potential for “stable” aspen communities. Model predictions were depicted spatially within GIS as probability of conifer encroachment. In addition, prediction‐conditioned fallout rates and receiver operating characteristic curves were used to partition the continuous model output. Categorical maps were then produced for each study site delineating potential “stable” and “seral” aspen community types using an overlay analysis with landcover maps of aspen‐conifer forests.

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Robertson, Andrew. "Investigating the causes and consequences of individual niche variation in group living badgers." Thesis, University of Exeter, 2012. http://hdl.handle.net/10871/9927.

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Individual niche variation is increasingly being demonstrated in animal populations in a wide variety of species and taxa. Niche variation among individuals has important implications for the ecology, evolution and management of animal populations and is a subject of increasing interest. However, despite its widespread occurrence the causes and consequences of individual niche variation remain poorly understood. In this thesis I use the European badger (Meles meles), a well studied species of high ecological interest, as a model system to investigate individual niche variation. In order to achieve this I combine information on individual foraging niches derived via stable isotope analysis (SIA) of badger vibrissae with detailed life history and ecological data from a long-term study population to investigate the incidence, cause and consequence of individual niche variation within badger social groups. First I use the biomarker Rhodamine B to investigate vibrissae growth rates and patterns in badgers and demonstrate that the isotopic composition of a single vibrissa likely reflects diet over several months (Chapter 2). Next I explore the use of SIA as a tool to investigate badger diet, by comparing isotopic patterns to seasonal changes in diet measured using faecal analysis (Chapter 3). My results provide validation that SIA is powerful tool for investigating foraging variation in this species, and suggest that within badger populations substantial dietary variation may occur among individuals. Further investigation of isotopic variation Indicates that individuals within social groups differ markedly and consistently in their isotopic signature, independent of age and sex effects and that in some instances these differences are remarkably consistent across year (Chapter 4).This suggesting long term individual specialisation (Chapter 4). I find that the degree of this individual specialisation, and the relationship between specialisation and body condition is influenced by competition for resources (Chapter 5). Social groups with higher levels of competition exhibit greater specialisation and specialised individuals within these highly competitive environments are in better condition. Finally, I discuss the implications of these results for individual niche variation, for the application of SIA to study this behaviour and for badger ecology generally (Chapter 6). I also outline future directions for further research.

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Bolte, Constance E. "NICHE CONSERVATISM OR DIVERGENCE: INSIGHTS INTO THE EVOLUTIONARY HISTORIES OF Pinus taeda, Pinus rigida, AND Pinus pungens." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4842.

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Environmentally related selective pressures and community interactions are well-documented drivers for niche differentiation, as natural selection acts on adaptive traits best fit for survival. Here, we investigated niche evolution between and within Pinus taeda, Pinus rigida, and Pinus pungens and sought to identify which climate variables contributed to species divergence. We also sought to describe niche differentiation across genetic groupings previously identified for P. taeda and P. rigida. Ecological niche models were produced using Maximum Entropy followed by statistical testing based on a measure of niche overlap, Schoener’s D. Both niche conservatism and niche divergence were detected, thus leading us to conclude that directional or disruptive selection drove divergence of the P. taeda lineage from its ancestor with P. rigida and P. pungens, while stabilizing selection was associated with the divergence of P. rigida and P. pungens. The latter implies that factors beyond climate are important drivers of speciation within Pinus.

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Walls, Bradley J. "Quantitative Paleobiogeography of Maysvillian (Late Ordovician) Brachiopod Species of the Cincinnati Arch: a Test of Niche Modeling Methods for Paleobiogeographic Reconstruction." Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1243010764.

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48

García-Villacorta, Roosevelt. "Integrating molecular biogeography and community ecology to understand the evolution of habitat specialization in Amazonian forests." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/11795.

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I investigated the origin of western Amazonian white-sand vegetation and the evolution of plant habitat specialization to different edaphic conditions in Neotropical lowland forests. In order to address these goals I used complementary ecological as well as molecular phylogenetic approaches. Amazonian white-sand forests harbour a flora specialized to nutrient-poor sandy soils, which is distributed as habitat-islands across the Amazon and Guiana Shield regions. This flora has been suggested to have many local and regional endemics, therefore making an important contribution to overall Neotropical plant diversity. The role of habitat specialization in the origin of this flora and its relationships with other floras within the Amazon- Guiana regions is not well understood. To shed light onto these questions, this thesis studies the floristic composition of these forests as well as molecular phylogenetic patterns of selected plant lineages containing white-sand species. The floristic study focused on the white-sand forests of the western Amazon region, which contained 1180 species of vascular plants whereas the non-white-sand Amazon and Guiana Shield dataset consisted of 26,887 vascular plant species. 77% of these species occurred outside white-sand habitats, in other habitat types of the Amazon region, while 23% were white-sand specialists. This demonstrates lower endemism in western Amazonian white-sand forests than previously estimated. 88% of the total westen Amazon white-sand specialist occur within the limits of the Guiana Shield region with the remaining 12% being endemics to the white-sand forests of the western Amazon. Within the Guiana-Shield region, Caquetá Moist Forests (56%), Guayanan Highlands (55%), and Negro-Branco Moist Forests (53%) were the biogeographic regions with the highest proportions of western Amazonian whitesand specialists. Cluster analysis of province level floristic checklists across the Amazon and Guiana regions showed that western Amazonian white-sand forests are nested within floras of the western Guiana-Shield region compared to other floras in the Amazon. Molecular phylogenetic analyses were carried out for the widespread and species-rich families Sapotaceae and Chrysobalanaceae, which display an uneven number of white-sand specialists. Sapotaceae had only three white-sand specialists but Chrysobalanaceae had a larger number of white-sand specialists (14 species). Phylogenetic analysis showed that white-sand specialist species in both studied families were scattered across the phylogenies. Both families show a marked absence of edaphic niche conservatism, suggesting that evolutionary switching amongst habitat types has been frequent. Ancestral state reconstruction of habitat specialization under a maximum likelihood approach suggests that preference for poor soils may be ancestral in these clades, especially in Chrysobalanaceae, but that the evolution of species entirely restricted to white-sand soils is in general much more recent and has multiple origins. For the white-sand flora of the western Amazon in particular, there is little evidence that it comprises ancient lineages as previously hypothesized. The historical construction of the Amazonian white sand flora is more likely to be the result of a gradual accumulation of species with different degrees of edaphic specialization, both by on-going speciation driven via habitat switching from non-white-sand specialists and via regional dispersal events after these habitats became available in regions such as the western Amazon. Edaphic transitions between different habitat types were not evolutionary constrained, which may have favoured edaphic niche evolution and the accumulation of plant species diversity in Neotropical lowland forests.

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Kulhanek, Stefanie. "Investigating the use of invasion history, meta-analysis and niche-based models as tools for predicting the ecological impacts of introduced aquatic species." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66655.

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Biological invasions pose a major threat to global biodiversity. While there is increasing concern regarding the impacts caused by non-indigenous species (NIS), generalisable tools for predicting their ecological effects have yet to be developed. Several researchers have suggested that examining the previously documented effects of NIS, termed invasion history, can serve as a basis for forecasting future impacts. Yet, while predictive models for impact have been devel oped based on the invasion histories of several widespread invaders, the generalisability of such approaches has not been demonstrated. The severity of the impacts caused by NIS may vary as a function of their local abundance across invaded sites. Thus by estimating the expected abundance of introduced species, at potential recipient locations, we may be able to identify habitats which are particularly vulnerable to their effects. While ecological niche-based models (ENM) have often been used to predict the abundance of species within their native ranges, such approaches have rarely been applied to NIS. In this thesis I conduct an extensive literature review, using 19 aquatic species, and assess the utility of invasion history for predicting future impacts. I illustrate that, while for most NIS limited and heterogeneous data currently inhibits the development of quantitative predictions, invasion history can often reveal the type and direction of future impacts. Using one of these species, Cyprinus carpio, as a case study, I conduct a meta-analysis and demonstrate that, where data is available, models incorporating NIS biomass can explain a substantial amount of variation in the severity of impacts across invaded locations. I then develop neural network-based ENM to forecast both the occurrence and biomass of C. carpio in a portion of its invaded range, using monitoring data from Minnesota. I test the ability of the resulting models to gene
Les invasions biologiques posent un risque majeur pour la biodiversité mondiale. Malgré qu'il y ait un intérêt grandissant concernant les impacts causés par les espèces non indigènes (ENI), des outils de prédictions de leurs effets écologiques restent encore à être développés. Plusieurs chercheurs ont suggéré que l'étude des impacts antérieurs des ENI, nommé historique d'invasion, pourrait servir en tant que référence pour prédire leurs effets futurs. Et malgré que des modèles de prédictions aient été développés selon l'historique d'invasion de certaines espèces envahissantes notoires, la précision globale de tels outils reste à être démontrée. La sévérité des impacts causés par les ENI peut varier selon leur abondance à travers des milieux envahis. Ainsi, par la prédiction de l'abondance des ENI, à travers des sites potentiellement envahissables, nous devrions être en mesure d'identifier les habitats particulièrement vulnérables face à leurs effets. En dépit que les modèles de niches fondées écologiques (MNE) aient souvent été utilisés pour prédire l'abondance des espèces dans leur aire de répartition d'origine, de telles approches ont rarement été mises en application envers des ENI. Dans cette thèse, j'entreprends une revue étendue des publications scientifiques concernant les ENI. En utilisant 19 espèces aquatiques comme échantillon, j'évalue l'utilité de l'historique d'invasion comme outil pour prévoir leurs impacts futurs. Je démontre que la plupart des données sur les impacts des ENI sont restreintes et hétérogènes, limitant le développement des prédictions quantitatives, mais que l'historique d'invasion peut souvent révéler le type et la direction et des impacts futurs. En utilisant un de ces ENI, Cyprinus carpio, comme sujet d'étude, je conduis une méta analyse et démontre que, où les données sont disponibles, les mod

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Subalusky, Amanda Lee. "The role of seasonal wetlands in the ecology of the American alligator." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1640.

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Dissertations / Theses on the topic 'Niche (Ecology)'

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