Dissertations / Theses: 'Invasie (biologie)'

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Vries, Johannes Erik de. "Genotypic and phenotypic effects of c-Ha-ras oncogene transfection on human colorectal carcinoma cell lines." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Maastricht University [Host], 1993. http://arno.unimaas.nl/show.cgi?fid=5752.

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Bardon, Clément. "Inhibition biologique de la dénitrification (BDI) par des métabolites secondaires du complexe d’espèces Fallopia spp." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10308/document.

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L'azote est souvent considéré comme le premier facteur limitant la croissance des plantes terrestres (Vitousek & Howarth, 1991a; LeBauer & Treseder, 2008). Ainsi, les études sur le contrôle du fonctionnement microbien et la sélection des microorganismes des sols par les plantes se sont principalement intéressées au cycle de l'azote (N) (Chapman et al., 2006). Certaines plantes peuvent inhiber la nitrification ou la minéralisation de l'azote des sols par la libération de métabolites secondaires. Cependant, bien que la dénitrification soit considérée comme une voie majeure de perte d'azote des sols (25-90%) (van der Salm et al., 2007; Radersma & Smit, 2011), l'inhibition de la dénitrification par les métabolites secondaires de plantes n'a jamais été démontrée. Or il a été constaté à de nombreuses reprises qu'aux voisinages de certaines plantes la dénitrification du sol était réduite. C'est le cas du complexe d'espèces Fallopia spp. pour lequel les principaux facteurs connus pour influencer ce processus ne pouvaient expliquer cette réduction (Dassonville et al., 2011). Nos résultats démontrent pour la 1ière fois que les plantes (ici Fallopia) peuvent inhiber la dénitrification par la libération de procyanidines de type B qui induisent en anaérobiose des modifications physiologiques chez les dénitrifiants. Selon les sols, les communautés peuvent être plus ou moins sensibles notamment en fonction de leur exposition précédente à Fallopia spp.. Nos résultats apportent de nouvelles connaissances sur les interactions entre plantes et microorganismes et améliorent notre compréhension sur la capacité des plantes à modeler le fonctionnement microbien des sols
Nitrogen is often considered as the first limiting factor of plant growth (Vitousek & Howarth, 1991a; LeBauer & Treseder, 2008). Thus studies on plant-driven microbial functioning and selection by secondary metabolites have mostly focused on the effect of plant on the nitrogen (N) cycle (Chapman et al., 2006). Some plants can inhibit the nitrification and the nitrogen mineralization processes in soils through the release of secondary metabolites (Subbarao et al., 2009; Dietz et al., 2013; Heumann et al., 2013). However, while denitrification is considered as a major way of N losses in soils (25-90%) (van der Salm et al., 2007; Radersma & Smit, 2011), the denitrification inhibition by plant secondary metabolites was never demonstrated. However, it has been observed several times that the denitrification in soils near some species was reduced. The invasive complex species Fallopia spp. was shown to reduce denitrification in soils without affecting principal factors known to control this process (Dassonville et al 2011). Our, results demonstrate for the first time, that plants (here Fallopia spp.) can inhibit denitrification through the release of B-type procyanidins that induce physiological changes in denitrifying bacteria under anaerobic conditions. These compounds affect specifically the membrane-bound NO3-reductase through conformational changes. Less sensitive soils denitrifying communities may be selected in soils previously exposed to Fallopia spp. Our finding provides new insight into plant-soil interactions and improves our understanding of plants abilities to shape microbial soil functioning

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Seyed, Sadr Mohamad. "SLIT proteins inhibit malignant brain tumour cell invasion via downregulation of pro-invasive genes." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110340.

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Most cancer deaths result from the progression of the tumour pathology whereby a localised mass evolves into an invasive and metastatic disease, spreading away from the main tumour mass. Malignant brain tumours such as glioblastoma and medulloblastoma are among the most invasive human cancers. The Slit-Robo pathway is extensively characterised as a repellent of axons and neural cells. Therefore we hypothesised that Slit proteins would repel invasive brain tumour cells. The first chapter of this thesis provides a thorough introduction of the oncology field as it pertains to malignant brain tumour biology and to the field of Slit-Robo family of proteins. The second chapter provides evidence for Slit proteins and their inhibitory effect on malignant brain tumour cell invasion. We further characterise the signaling pathway employed by Slit proteins to impart an inhibitory effect on tumour cell invasion. We present data suggesting that Slit proteins decrease the transcriptional expression of numerous pro-invasive and pro-angiogenic genes in malignant brain tumour cells. We characterise the product of one of these genes, MMP14, as a protease of Robo proteins. A model is proposed that explains the observation that decreasing the expression of MMP14 leads to a decrease in brain tumour cell invasion. These results suggest that malignant brain tumour cells respond to Slit by modulating a series of transcripts critical for cell invasion. Therefore, targeting malignant brain tumour cells with Slit proteins or chemical analogues that mimic Slit's effects may provide a potentially novel anti-invasive therapy.
La transformation d'une tumeur primaire en tumeur maligne et métastatique, s'éloignant du point d'origine, est souvent la principale cause de décès chez le patient. Les tumeurs cérébrales malignes tel les glioblastomes et les médulloblastomes sont parmi les plus invasives cancers humains. La voie de signalisation de Slit-Robo a été largement caractérisée et montre l'implication de Slit-Robo dans la répulsion des axones et cellules neuronales. Dans cette étude, nous avons étudié la possibilité que Slit-Robo pourraient repousser les cellules cancéreuses invasives cérébrales. Le premier chapitre de cette thèse présente une introduction approfondie du rôle de la famille des protéines Slit-Robo dans le contexte du cancer et de la biologie des tumeurs cérébrales. Le deuxième chapitre présente des preuves de l'implication des protéines Slit et leur rôle dans l'inhibition de l'invasion des cellules de tumeurs cérébrales. Aussi, la caractérisation de la voie de signalisation employée par les protéines Slit dans l'inhibitionde l'invasion des cellules cancéreuses a été montrée. De plus, cette étude présente des résultats qui suggèrent que les protéines Slit diminuent l'expression de la transcription degènes pro-angiogénique et pro-invasif des cellules tumorales. Nous avons aussi identifié MMP14 comme une protéase des protéines Robo et dont l'expression est influencée par les protéines Slit. Finalement, nous proposons un modèle démontrant qu'une diminution de l'expression de MMP14 induit une réduction de l'invasion des cellules tumorales du cerveau.

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Cohen, Gabriel Jorgewich. "Genética de populações aplicada à biologia da invasão: um panorama da invasão da rã-touro (Lithobates catesbeianus)." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/41/41133/tde-26062018-091821/.

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Invasões biológicas tem um papel cada vez mais importante nas políticas ambientais, visto que espécies invasoras desempenham uma crescente influência sobre novos ambientes onde são introduzidas, podendo gerar grandes impactos naturais e financeiros. Estudos na área da biologia da invasão se fazem extremamente necessários para remediar e evitar novas introduções. Dentre as metodologias aplicadas ao estudo das invasões biológicas, a genética de populações apresenta diversas ferramentas uteis para responder perguntas relevantes nos esforços de controle de espécies invasoras. No presente trabalho usamos recursos moleculares aplicados à genética de populações da rã-touro (Lithobates catesbeianus), o anfíbio invasor mais disseminado no planeta. Através deste estudo foi possível compreender mais sobre a estrutura genética das populações invasoras do Brasil e do mundo, além de seu histórico de invasão e sua população nativa de origem. Entender e contextualizar as características e motivos que levam ao sucesso de uma invasão biológica é importante para esforços de combate a pragas e para evitar que outros invasores se fixem em novos ambientes. Este trabalho levantou novos conhecimentos que podem e devem ser usados em políticas de combates à invasão da rã-touro
Biological invasions play an increasingly important role in environmental policies as invasive species represent a growing impact in new environments where they are introduced, potentially causing large natural and financial problems. Studies in the field of invasion biology are extremely necessary to remedy and prevent new introductions. Among the methodologies applied to the study of biological invasions, population genetics presents several useful tools to answer relevant questions in efforts to control invasive species. In the present work we used molecular resources applied to the genetics of populations of the American Bullfrog (Lithobates catesbeianus), the most widespread invasive amphibian on the planet. Through this study it was possible to understand more about the genetic structure of the invasive populations in Brazil and in the world, and its history of invasion and its native population of origin. Understanding and contextualizing the characteristics and motives that lead to the success of a biological invasion is important for pest control efforts and to prevent other invaders from focusing on new environments. This work has raised new knowledge that can and should be used in policies to combat Bullfrog invasion

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Bohl, Kerry. "An investigation of the factors leading to invasion success of non-native plants using a system of native, introduced non-invasive, and invasive Eugenia congeners in Florida." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4442.

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The overwhelming majority of plant species introduced into a new range never become invasive. Consequently, identification of factors allowing the small fraction of successful invaders to naturalize, increase in abundance, and displace resident species continues to be a key area of research in invasion biology. Of the considerable number of hypotheses that have been proposed to resolve why some plant species become noxious pests, the enemy release hypothesis (ERH) is one of the most commonly cited. The ERH maintains that invasive plants succeed in a new range because they are no longer regulated by their coevolved natural enemies, and this reduction in enemy pressure imparts a competitive advantage over native species, which continue to be negatively impacted by top-down processes. Alternatively, the ability of invasive plant species to outperform their counterparts, rather than escape from enemies, may be key in conferring invasion success. The importance of preadapted traits and release from natural enemies in successful invasion remains unclear, likely owing to a lack of empirical studies comparing their effects on relative performance and population growth of closely related species that differ in origin and invasiveness. A system of co-occurring native, introduced non-invasive, and invasive Eugenia congeners exists in south Florida, providing an opportunity to address deficiencies in our understanding of plant invasions by investigating the factors leading to invasion success for Eugenia uniflora. This approach is novel because very few studies have simultaneously incorporated both native and introduced non-invasive congeners into tests of these hypotheses, and no others have done so using this system of Eugenia congeners. The first study in this dissertation tested the ERH using an insect herbivore exclusion experiment in the field to compare the effects of natural enemies on the performance and population growth of Eugenia uniflora and its native congeners. The results showed that E. uniflora sustained more herbivore damage than its native counterparts, and that the effects of herbivores were sufficient to have negative impacts on performance and population growth. In sum, these findings contradict the ERH. Surprisingly, the vast majority of damage to E. uniflora was caused by the recently introduced Sri Lankan weevil (Myllocerus undatus), with which it shares no coevolutionary history. The second study compared seedling performance among native, introduced non-invasive, and invasive Eugenia congeners to determine if the success of E. uniflora can be attributed to superior performance traits. Invasive E. uniflora was found to outperform its native and introduced non-invasive counterparts in a number of seedling traits, including emergence, growth, and survival, in spite of sustaining higher levels of herbivore damage in the field. This result was consistent across years and sites, suggesting that superior performance may be an important factor in invasion success by E. uniflora. The final experiment investigated the role of enemy release on performance of native, introduced non-invasive, and introduced invasive Eugenia seedlings using an insect herbivore exclusion experiment in the field. In this study, the invasive E. uniflora was again found to sustain more damage by foliar herbivores compared to its native and introduced non-invasive counterparts. However, in spite of higher levels of herbivore damage, E. uniflora continued to outperform its congeners in terms of stem growth, and its congeners did not outperform E. uniflora in any attribute. Insect herbivores negatively affected survival of all species, but were found to have little effect on growth. In combination, the results of these studies indicate that the ability of E. uniflora to outperform its native and introduced congeners at the seedling stage, and not release from insect herbivores, may contribute to its success as an invader. Additionally, E. uniflora exhibits relatively low resistance to herbivory in the new range, and instead may possess an ability to tolerate moderate levels of damage. The implications of this study are that enemy release may not be important in determining invasion success in some systems, and that the accumulation of new enemies may mitigate the effects of invasive plants over time. The paucity of studies investigating interactions among invasive plants and herbivores that share no coevolutionary history warrants further research. Finally, this system of Eugenia congeners provides valuable opportunities to test additional hypotheses and to further explore factors leading to invasion success.

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Barrios, Barri Oriol de. "Role of ZEB1 in Tumor Progression: Regulation of Cell Invasion and Senescence." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/401707.

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The members of ZEB family of transcription factors (ZEB1 and ZEB2) are widely known for its role in epithelial-to-mesenchymal transition (EMT), a highly relevant process during development and tumor progression. In this process, cells lose their epithelial features and acquire mesenchymal markers, thus increasing their motility and invasive capacity. However, it has been recently described that ZEB factors can function beyond the EMT induction, and that are associated with other tumor hallmarks: apoptosis inhibition, chemotherapy resistance, etc. Regarding colorectal cancer (CRC), ZEB1 is activated by the Wnt signaling pathway, which is active in around 80% of the cases. Consequently, ZEB1 is expressed in the invasive cells at the tumor front, providing the tumor with higher aggressiveness and metastatic capacity. Taking this background into account, the general aim of the Thesis was to characterize new potential mechanisms through which ZEB1 regulates oncogenic transformation and tumor progression in CRC, beyond EMT induction. The specific aims were: 1) Describe the role of ZEB1 in the regulation of initial steps of tumor invasiveness, such as the remodeling of the extracellular matrix (ECM); 2) Identify new ZEB1 target genes at the tumor front of CRCs, investigating a potential modulation of Wnt signaling, as well as characterizing the in vivo relevance of these potential targets; 3) Identify other hallmarks of cancer that may be regulated by ZEB1 during CRC progression. The results of the Thesis are presented as a summary of publications. The first paper (Clin Cancer Res, 2013. 19(5):1071-82) describes the role of ZEB1 in the opposite regulation of the Plasminogen Activation System (PAS) members (uPA and PAI-1). This regulation promotes the migration of CRC cells through the ECM. The conclusions obtained from this first paper are: 1- ZEB1 modulates CRC cells migration through the peritumoral stroma by means of uPA activation and PAI-1 repression 2- ZEB1 activates uPA at the transcriptional level through its direct binding to the promoter region, in a mechanism involving the coactivator p300 and Wnt signaling. 3- ZEB1 represses PAI-1 by reducing its mRNA stability, which supposes a new gene regulation mechanism for ZEB1. 4- During ZEB1-induced CRC cells migration and invasion, uPA expression is required. 5- ZEB1 correlates positively with uPA, but not with PAI-1, at the invasive front of CRCs, cooperating in its role in ECM remodeling. The results of the second paper (Gut, 2016. doi:10.1136/gutjnl-2015-310838) have identified a new mechanism through which ZEB1 inhibits cancer cells entrance in senescence, a tumor suppressor mechanism. ZEB1 activates the Wnt-antagonnist DKK1, triggering the activation of a signaling cascade that involves mutant p53, MDM2 and CtBP. This ultimate corepressor cooperates with ZEB1 in the repression of macroH2A1, key in senescence induction. The conclusions obtained from this second paper are: 1- The maximum effect of ZEB1 in predicting poor CRC survival requires high Wnt- antagonist DKK1 simultaneous expression. Both genes correlate positively in CRCs. 2- ZEB1 activates DKK1 transcriptionally, through a mechanism that involves the coactivator p300 and the Wnt-effector TCF4. 3- The combined expression of ZEB1 and DKK1 inhibits a senescence-related genes group in CRC patients. Some of these genes, including H2AFY (that codifies for macroH2A1), are cooperatively repressed by ZEB1 and DKK1. 4- ZEB1 requires the presence of DKK1 to repress the formation of senescence- associated heterochromatin foci and the consequent cellular senescence. 5- ZEB1 represses macroH2A1 by direct binding to its promoter. 6- ZEB1 represses cellular senescence through the subsequent activation of DKK1, mutant p53, MDM2 and CtBP. The activation of CtBP enhances ZEB1’s repressor activity on macroH2A1 promoter. 7- ZEB1 correlates positively with DKK1 at CRC tumor front. Conversely, macroH2A1 displays an inverse expression pattern. 8- Reduction of ZEB1 levels in vivo is sufficient to induce senescence, reduce colorectal tumor formation and improve survival in a mouse model of CRC. 9- The tumorigenic capacity of ZEB1 depends on the concomitant low levels of macroH2A1. 10- The role of ZEB1 in determining poor CRC prognosis depends on its ability to repress macroH2A1 and other senescence markers, such as GLB1.
Els factors de transcripció ZEB (ZEB1 i ZEB2) son àmpliament coneguts pel seu paper en la transició epitelial-mesenquimal (EMT). A través d’aquest procés, les cèl·lules perden les característiques que les defineixen com a epitelials i adquireixen marcadors mesenquimals, augmentant així la seva capacitat invasiva. Tot i això, recentment s’ha descrit que els factors ZEB tenen funcions més enllà de l’EMT, com ara la resistència a la quimioterapia, que promouen la progressió tumoral. En el cas del càncer colorectal (CCR), s’ha descrit que ZEB1 és activat per la via de senyalització de Wnt, activa en un 80% dels casos. En conseqüència, ZEB1 s’expressa en les cèl·lules invasives del front tumoral. Tenint en compte aquests antecedents, l’objectiu general de la Tesi ha estat el de caracteritzar nous mecanismes a través dels quals ZEB1 regula la transformació oncogènica i la progressió tumoral en CCR, més enllà de la inducció de l’EMT. Els objectius específics han estat: 1) descriure el paper de ZEB1 en la regulació de les etapes inicials d’invasivitat, com la remodelació de la matriu extracel·lular; 2) identificar nous gens diana de ZEB1 al front tumoral de CCR, així com caracteritzar la rellevància d’aquestes dianes in vivo; i 3) identificar processos comuns a tots els tipus de càncer que puguin estar regulades per ZEB1 en la progressió del CCR. Els resultats es presenten com a compendi de publicacions. En el primer dels articles (Clin Cancer Res, 2013. 19(5):1071-82), es descriu el paper de ZEB1 en la regulació oposada dels membres del sistema activador del plasminogen (uPA i PAI-1). Aquesta regulació promou la migració de les cèl·lules a través de la matriu extracel·lular. En el segon dels articles (Gut, 2016. doi:10.1136/gutjnl-2015-310838), s’ha identificat un nou mecanisme a través del qual ZEB1 està inhibint l’entrada de les cèl·lules tumorals a l’estat de senescència, un conegut mecanisme supressor tumoral. ZEB1 activa l’inhibidor de la via Wnt DKK1, desencadenant l’activació d’una ruta de senyalització que implica a p53 mutat, MDM2 i CtBP. Aquest darrer coopera amb ZEB1 en la repressió de la histona macroH2A1, clau en la inducció de la senescència.

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Poidatz, Juliette. "De la biologie des reproducteurs au comportement d’approvisionnement du nid, vers des pistes de biocontrôle du frelon asiatique Vespa velutina en France." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0778/document.

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Cette thèse CIFRE porte sur la biologie, le comportement et le biocontrôle du frelonasiatique Vespa velutina, un prédateur invasif d’abeilles. Depuis son introduction en France, ce frelonétend maintenant son aire de répartition en Europe, impactant à la fois l’environnement etl’apiculture. L’objectif de ces travaux sera d’enrichir le savoir sur cette espèce pour perturber ledéveloppement des colonies de V. velutina à différents niveaux afin d’en limiter la prolifération. Lepremier axe porte sur la biologie des reproducteurs de V. velutina, afin d’empêcher la fondation decolonies en amont. Ce travail précise les données concernant la maturation sexuelle des mâles de V.velutina, compare certains traits liés à la fertilité des fondatrices avec celles du frelon européen, etmet en évidence une plus grande précocité et fertilité de V. velutina. Le deuxième axe porte sur labiologie des colonies, de la collecte à la distribution des ressources dans le nid. A l’aide de pucesélectroniques marquant des ouvrières (technique RFID), nous avons mesuré le rayon d’action et seslimites chez les ouvrières V. velutina. En marquant de la nourriture avec des métaux lourds, nousavons pu suivre l’évolution de sa distribution dans les colonies suivant leur structure. Le troisièmeaxe porte sur le biocontrôle de V. velutina avec des champignons entomopathogènes. Nous avonsévalué l’efficacité de différents isolats et de leur mode d’application contre V. velutina, puis décrit unchampignon naturellement parasitant V. velutina. Ces travaux ont permis de faire avancer lesconnaissances sur la biologie et la physiologie des frelons, mais également de proposer des pistes decontrôle durable de l’invasion européenne de V. velutina
This CIFRE thesis deals with the biology, the behavior and the biological control of aninvasive predator of bees, the hornet Vespa velutina. Since its introduction in France, this hornet isnow invading most countries in occidental Europe, dealing damages both to the environment and thebeekeeping activity. In order to limit its proliferation, a good strategy could consist in disrupting itscolony development at different levels, explored in this work. The first axis deals with V. velutinareproductive biology, exploring the different paths to prevent colonies creation. First we describedthe sexual maturation of males in V. velutina, and second we compared different traits linked tofertility between foundresses of V. velutina and the European hornet, thus highlighting V. velutinahigher precocity and fertility potential. The second axis explored the biology of colonies, fromresource collection to resource distribution in the nest. Using RFID technic, we assessed the actionrange and its boundaries in V. velutina workers. We also labelled food and observed its distribution inV. velutina colonies in function of the colony size and structure. The third axis deals with V. velutinabiocontrol, using entomopathogenic fungi. We evaluated the efficiency of different isolates anddifferent application methods on V. velutina, and described a wild fungus found naturally parasitizingV. velutina. This work brought knowledge on biology behavior and physiology of this invasive hornet,and also proposed options that could be assayed for a durable control of V. velutina

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Cosette, Jérémie. "Design and optimization of small animal non-invasive imaging approaches for evaluating the effects of innovative treatments of Primary Central Nervous System Lymphomas." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05T069/document.

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Pas de résumé en français
Primary central nervous system lymphomas (PCNSL) are very aggressive malignancies with poor survival rate even with treatments (survival median is 44 months). This disease affects immune cells (lymphocytes) and forms diffuse and non-surgically removable tumor in the central nervous system. High-dose chemotherapy and radiotherapy are the common treatments with severe side effects. New therapeutic approaches are required for increasing treatment efficiency. We focused on primary intraocular lymphomas (PIOL) and primary cerebral lymphomas (PCL), which are subtypes of PCNSL. PIOL and PCL cells have a high propensity to migrate and form metastases in the brain and in the controlateral eye in the case of PIOL, and in the eye in the PCL case. However, metastatic dissemation mechanisms remain unclear. The objective of the present work was to study the effects of innovative treatments of B-cell lymphoma on primary tumor, on metastases, and on circulating tumor cells in PIOL and PCL immunocompetent syngeneic murine models of lymphomas using non-invasive in vivo imaging methods. We studied the effects of Ublituximab, a glycoengineered anti-CD20 monoclonal antibody (mAb), and CpG-ODN, a TLR-9 agonist, in mouse models. We showed that Ublituximab exhibits significant anti-tumor effect in PIOL and PCL, while CpG showed significant anti-tumor effect in PCL. We monitored the tumor burden and metastases using innovating non-invasive optical imaging or cell detection methods: bioluminescence imaging (BLI) and in vivo flow cytometer (IVFC). BLI was used to locate metastasis and to quantify tumor burden. We indeed developed a bioluminescence-based tumor burden quantification method that reduces user-dependence, allows comparisons between experiments, reveals statistical relevance, and which is easy to use. An IVFC device was set up to investigate the role of circulating tumor cells (CTCs) in PIOL and PCL. This fluorescence-based technique allows detection of CTCs by analyzing the cells flowing in blood vessels. However we had to overcome the problem of autofluorescence and tissue absorption. Two approaches were studied in parallel: a elaborating new cell line expressing far red fluorescent proteins, modulating the excitation light of an IVFC device to give the cell a unique signature therefore enhancing sensitivity, increasing signal to noise ratio. The modulated excitation IVFC allowed us to calculate the velocity of cells, and infer their position in blood vessel phantoms. The analysis of treatment effects on tumor burden, metastases and CTCs in PIOL and PCL could help understanding lymphoma metastatic dissemination and contribute to treatment follow-up, thus allowing design of new therapeutic approaches with increased efficacy

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Pérez, Fusté Noel. "Mecanismes de regulació de l'adhesió i la invasió cel·lulars pel complex ciclina D1-Cdk4 citoplasmàtic." Doctoral thesis, Universitat de Lleida, 2016. http://hdl.handle.net/10803/399572.

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El rol més conegut de ciclina D1 és com a regulador del cicle cel·lular i la proliferació, però diversos estudis suggereixen que ciclina D1 també interacciona amb proteïnes citoplasmàtiques involucrades en la regulació de la migració i la invasió cel·lulars. En aquest treball es mostra que la paxilina, una proteïna dels focus d'adhesió implicada en la regulació de l’adhesió i la migració, és un substrat citoplasmàtic del complex ciclina D1-Cdk4. Aquest complex fosforila una fracció de paxilina que es troba associada a la membrana cel·lular i promou l'activació de la GTPasa Rac1, induint la migració i la invasió cel·lulars. A més, per avaluar la funció citoplasmàtica de ciclina D1 de manera independent de la funció nuclear, hem construït un mutant de ciclina D1 que s’uneix a la membrana cel·lular i segresta ciclina D1 en el citoplasma, fent que les cèl·lules tumorals que expressen aquest mutant tinguin major potencial invasiu i metastàtic.
El rol más conocido de ciclina D1 es como regulador del ciclo celular y la proliferación, pero varios estudios sugieren que ciclina D1 también interacciona con proteínas citoplasmáticas involucradas en la regulación de la migración y la invasión celulares. En este trabajo se muestra que la paxilina, una proteína de los focos de adhesión implicada en la regulación de la adhesión y la migración, es un sustrato citoplasmático del complejo ciclina D1-Cdk4. Este complejo fosforila una fracción de paxilina que se encuentra asociada a la membrana celular y promueve la activación de la GTPasa Rac1, induciendo la migración y la invasión celulares. Además, para evaluar la función citoplasmática de ciclina D1 de manera independiente de la función nuclear, hemos construido un mutante de ciclina D1 que se une a la membrana celular y secuestra ciclina D1 en el citoplasma, haciendo que las células tumorales que expresan este mutante tengan mayor potencial invasivo y metastásico.
The best known role of cyclin D1 is as a regulator of cell cycle and proliferation, but several studies suggest that cyclin D1 also interacts with cytoplasmic proteins involved in the regulation of cell migration and invasion. This work shows that paxillin, a protein of the focal adhesions involved in the regulation of adhesion and migration, is a cytoplasmic substrate of cyclin D1-Cdk4 complex. This complex phosphorylates a fraction of paxillin that is associated to the cell membrane and promotes the activation of Rac1 GTPase, inducing cell migration and invasion. In addition, to evaluate the cytoplasmic function of cyclin D1 independently of the nuclear function, we constructed a mutant of cyclin D1 which binds to the cell membrane and sequesters cyclin D1 in the cytoplasm, making the tumor cells that express this mutant more invasive and metastatic.

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Soley, Nathan. "Reproductive Biology of the invasive plant Elaeagnus umbellata: breeding system, pollinators, and implications for invasive spread." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1164.

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Reproductive studies in invasive plants are necessary for an understanding of their potential to establish and spread in foreign environments. Elaeagnus umbellata Thunb. (autumn olive) is an invasive woody shrub that flowers early in the spring and is often noted for its abundant fruit set. This study examined the reproductive biology of E. umbellata in Illinois, where it is highly invasive. Hand-pollination experiments were performed to determine the breeding system of E. umbellata, and floral visitors were collected to determine its pollinators. Experiments showed that E. umbellata is a predominantly outcrossing species with a self-incompatible breeding system. However, individual variation was detected in several reproductive characteristics. Pollen tube analyses revealed that a small percentage of individuals allow successful self-pollen tube growth, and self-fruit set resulting from automatic self-pollination (autogamy) was relatively high in a few plants. Automatic self-pollination is possible because the male and female parts of flowers mature sychronously, but the likelihood of autogamy may vary among individuals due to variability in the spatial separation of male and female parts (herkogamy). Variability in the incompatibility system and the level of herkogamy may impact the outcrossing rates and reproductive success of individuals. The majority of floral visitors to E. umbellata were generalist pollinators. Frequently visiting bees included small and large species such as native Andrena spp., Augochlorella aurata, Bombus spp., Ceratina calcarata, Xylocopa virginica, and the introduced Apis mellifera. Bombylius major (large bee fly) and the moth Mythimna unipuncta (armyworm) were also frequent visitors. Most of the above insect taxa are pollinators of E. umbellata based on analysis of pollen on insect bodies. E. umbellata is likely to achieve its abundant fruit set where these common pollinators and other E. umbellata are present. However, in my study sites, many individuals experienced low fruit set on branches that were open to pollinator visitation, suggesting pollen limitation may be common in some years and at certain sites. The discovery of autogamous individuals demonstrates that some E. umbellata individuals may be able to establish and spread even when mates or pollinators are limiting.

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Bäucker, Cornelia [Verfasser]. "Interactions of invasive plants with soil biota / Cornelia Bäucker." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1032899352/34.

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Rius, Viladomiu Marc. "Biologia i genètica de poblacions de l'ascidi invasor "Microcosmus squamiger"." Doctoral thesis, Universitat de Barcelona, 2008. http://hdl.handle.net/10803/813.

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En les últimes dècades hi ha hagut una creixent conscienciació sobre l'efecte que les invasions biològiques poden tenir en la biodiversitat mundial. Així, avui en dia l'impacte de les espècies invasores és considerat com una de les principals amenaces per als ecosistemes natius, així com també per a l'economia mundial. Recentment hi ha hagut un accelerament en els canvis soferts pels ecosistemes marins a causa de espècies invasores, especialment en les zones costaneres.
Aquesta tesi doctoral té com objectiu estudiar la biologia, l'ecologia i la genètica de les poblacions de l'espècie Microcosmus squamiger, un organisme marí que ha estat introduït en diversos llocs del món i que ha esdevingut invasor en algunes regions. L'estratègia multidisciplinària utilitzada en la present dissertació té com objectiu crear un ampli estudi d'aquest organisme que englobi el màxim de punts de vista sobre la seva biologia.
Les espècies exòtiques han estat identificades com una de les principals amenaces per a la conservació de la biodiversitat i el funcionament dels ecosistemes en sistemes marins. Els organismes marins han estat dispersats pels oceans sobretot des del moment en què els homes va començar a navegar pels mars. L'augment dels viatges transoceànics durant l'últim segle ha provocat un increment en la ritme d'introduccions d'espècies exòtiques marines, especialment en zones costeres.
L'espècie objectiu de la tesi és l'ascidi Microcosmus squamiger. Els ascidis són un component comú en comunitats bentòniques d'arreu del món, on viuen fixats a un substrat que tan potser natural com artificial. Encara que la majoria d'ascidis tenen una capacitat de dispersió molt limitada i efímera a nivell de la fase de larva planctònica, les larves poden ser sovint xuclades per les bombes de llast i ser desplaçades cap a dins dels tancs de la nau. Alternativament, les larves es poden assentar a alguna estructura com ara una deriva d'algues flotants o deixalles soltes que poden ser bombades cap al interior del vaixell. A més, els adults poden ser transportats en els cascs dels bucs propagant les seves larves en els llocs on aquests bucs fan parada - la majoria dels ports comercials i esportius. Els ascidis són cada vegada més reconeguts com un dels principals grups pel què fa a invasions marines a tot el món. Tenen capacitat de desplaçar altres organismes sèssils i d'alterar el funcionament dels ecosistemes de moltes maneres diferents.
Els marcadors genètics han estat proposats com una eina molt útil pel seguiment de la distribució de les espècies invasores, i s'han utilitzat sobretot en estudis filogeogràfics. Els estudis filogeogràfics poden revelar el seu/s origen/s i les vies d'introducció, que solen ser complexos a causa de la possibilitat de múltiples introduccions a partir d'una o més regions donants. Dos marcadors comuns utilitzats per a respondre a tals preguntes són l'ADN mitocondrial i els microsatèl·lits.
En la present dissertació hem emprès una àmplia gamma d'estudis centrats en M. squamiger incloent la taxonomia, trets biològics i ecològics de l'espècie i genètica de poblacions.
Conclusions finals
1. Diversos estudis taxonòmics han identificat erròniament M. squamiger i M. exasperatus. El present estudi posa en relleu la importància de la taxonomia per a l'estudi de les espècies invasores.
2. M. squamiger ha estat introduït amb èxit i ha colonitzat moltes regions de tot el món, en la seva majoria de clima mediterrani.
3. Els vaixells són el mètode més probable per a la dispersió transoceànica de M. squamiger.
4. Diverses colonizations no independents han constituït la composició actual de la poblacions introduïdes, que són genèticament tan diverses com les poblacions autòctones.
5. L'origen més probable de les poblacions introduïdes de M. squamiger són diferents regions d'Austràlia, principalment la regions oriental i occidental.
6. Les poblacions de M. squamiger a la regió Atlanto-Mediterrània mostren en general poca diferenciació genètica i cap particular estructura genètica associada a l'estret de Gibraltar. El baix nivell de diferenciació genètica entre poblacions és probable que sigui resultat de l'efecte combinat d'una alta connectivitat entre poblacions, a causa del transport marítim, i el poc temps transcorregut des de que M. squamiger va ser introduït a la regió (a mitjans del segle XX).
7. En el mar Mediterrani M. squamiger es distribueix exclusivament en la part occidental. Està present durant tot l'any i mostra una dinàmica poblacional fortament determinada per les estacions meteorològiques amb un cicle de vida de 2 anys, la qual cosa indica que aquesta espècie s'ha adaptat bé al nou entorn.
8. Les altes densitats de M. squamiger trobades (> 500 ind m-2, amb pics de fins a 2300 ind m-2) es mantenen al llarg de l'any en hàbitats naturals del mar Mediterrani, on aquesta espècie pot formar una densa capa monoespecífica que cobreix la major part del substrat disponible.
9. El cicle reproductiu de les poblacions de M. squamiger en el mar Mediterrani és estacional, sent la maduració de les gònades a la primavera i el principal moment de fresa a l'estiu.
10. Les espècies invasores marines tenen el potencial d'afectar les interaccions a nivell de l'assentament i del post-assentament amb espècies natives i, per tant, modificar la dinàmica poblacional nativa, tal com ens mostra el treball experimental amb M. squamiger i S. plicata.
11. Hi ha una necessitat clara de controlar M. squamiger ja que aquesta espècie colonitza ambients naturals i forma grans agregats que són una amenaça per a les comunitats natives i les activitats econòmiques humanes (p.ex. els cultius de bivalves).
The impacts created by invasive species are today considered one of the main threats to global biodiversity. Marine organisms have predominantly been moved around the world's oceans since people first began navigating the seas, and the increase in transoceanic travel during the last century has seen a concurrent rise in the rate of introductions of alien marine species. Ascidians are a common component of rocky shore communities worldwide. Although most ascidians have a very limited larval dispersal and a short-lived planktonic larval stage, they can often be caught in ballast pumps and settle within the ship. Alternatively, adults can be transported on hulls and sea chests of ships whereby they continue to spread their larvae. Genetic markers have been proposed as a very useful tool for monitoring and tracking the distribution of invasive species.
This PhD thesis aims to undertake a multidisciplinary study of the species Microcosmus squamiger, an ascidian species that has been introduced in several locations around the world and that has become invasive in some regions. The most relevant results of this dissertation are as follows. We found that taxonomic studies have misidentified M. squamiger and Microcosmus exasperatus. Our genetic results show that M. squamiger has successfully colonized many regions around the world, and that the most probable method of transoceanic dispersal of M. squamiger is through shipping. Different source areas from Australia are the most likely origin of M. squamiger introduced populations and non-independent colonizations have shaped the present composition of the introduced populations. We found that M. squamiger is found exclusively in the western region of the Mediterranean Sea and is present all year round with a 2-year life cycle. From experimental work involving M. squamiger and Styela plicata, we concluded that marine invasive species have the potential to affect settlement and post-settlement interactions with native species and therefore alter the native population dynamics. In conclusion, there is a need to control M. squamiger as this species colonizes natural environments and forms large aggregates that are a threat to native communities as well as human economic activities.

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Böhme, Katja [Verfasser], and Petra [Akademischer Betreuer] Dersch. "Identification and characterization of regulatory factors and regulatory RNA elements controlling the expression of the primary invasion factors invasin and YadA in Yersinia pseudotuberculosis / Katja Böhme ; Betreuer: Petra Dersch." Braunschweig : Technische Universität Braunschweig, 2010. http://d-nb.info/117582514X/34.

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Kelley, Amanda. "The Effect of Temperature on Phenotypes of the Invasive European Green Crab: Physiologic Mechanisms that Facilitate Invasion Success." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1004.

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Invasion physiology is an emerging field that endeavors to understand the influence of physiological traits on the establishment of non-native species in novel environments. The invasive European green crab,Carcinus maenas, is one of the world's most successful aquatic invaders, and is currently distributed across temperate marine ecosystems globally. The work presented here explored the thermal physiology of this species, and has highlighted several physiological traits that have likely influenced establishment success. Intraspecific comparisons of crabs sampled from the northern and southern edges of their recipient, or invaded range on the west coast of North America have identified both organismal and cellular physiological difference with respect to upper and lower thermal tolerances. Crabs sampled from British Columbia, Canada (BC) had a significantly lower mean upper thermal tolerance threshold and heat shock protein synthesis, Hsp70, compared to their warm acclimated conspecifics sampled from California (CA). These differential physiologic responses may be rooted in the disparate natural thermal habitats that each population occupies within their respective environments. The ability of this species to extend its current range limits was also investigated. Range expansion to the south has been limited, and is likely restricted by this species lack of adaptation to warmer temperatures. Because range expansion has been chiefly northward, characterizing this species' response to cold stress can identify whether colder temperatures poleward may limit further range expansion. Cold tolerance capacity was determined in the laboratory, and crabs sampled from Vancouver Island, British Columbia were able to withstand the over-wintering thermal regime that occurs in Sitka, Alaska, a site that is currently beyond the range limits of this species. Furthermore, intraspecific assessments found that the cold acclimated BC population exposed to cold shock significantly down regulated protein levels of cyclin D1, cell cycle modulator. Distinct differences in carapace width (CW) were detected along the thermal gradient present in the green crabs' range. This variation in body size was utilized to the test the temperature size rule hypothesis for ectotherms. Simply stated, the temperature size rule is the tendency for ectotherms to develop slower but mature to a larger body sizes at cooler temperatures. The results supported this hypothesis as crabs sampled from the warm portion of the range were found to be smaller than crabs sampled from the colder portion of the range. This pattern was detected along the native range as well. Differences in body size have the potential to influence the scope of invasion; larger individuals are generally more fecund and longer lived, which can increase both the intensity and frequency of larval dispersal that could further propel range expansion. The physiologic properties that the green crab possesses which may influence invasion success were examined using peer-reviewed literature with the aim of determining if these physiological traits confer invasion success across taxa. This analysis tested four hypotheses: 1) Broad geographic temperature tolerances (thermal width) confer a higher upper thermal tolerance threshold when comparing invasive and native species. 2) The upper thermal extreme experienced in nature is correlated with upper thermal tolerance threshold. 3) Protein chaperone expression, a cellular mechanism underlying thermal tolerance threshold, is greater in invasive organisms than in native ones. 4) Acclimation to higher temperatures can promote a greater range of thermal tolerance for invasives compared to natives. These preliminary results generally support the four stated hypotheses, and provide a solid foundation for further studies to explore and identify physiologic traits that facilitate invasion success. Overall, these studies investigated the thermal physiology ofCarcinus maenasfrom an invasive metapopulation and have brought about significant advances in our understanding of what physiologic traits correlate to invasion success in this species. In addition, the data presented here can aid resource managers in identifying habitats, based on thermal tolerance measurements that fit the criteria for invasion. Understanding how invasive organisms vary with respect to thermal tolerance can aid our understanding the patterns and processes of species invasions.

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15

Beckmann, Michael [Verfasser]. "In Search of Similarities in Invasive Plant Species - Comparing Native and Invasive Populations of Six Clonal Plant Species in Germany and New Zealand / Michael Beckmann." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1153400855/34.

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16

Church, Kathleen. "Agonistic interactions between invasive aquatic species." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86980.

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Species invasions threaten the integrity of biotic communities, as invaders may outcompete and replace resident species. For many aquatic invaders, species replacements are driven by aggression. I explored this phenomenon through a quantitative synthesis and laboratory experiments. A quantitative synthesis of published studies on aggression in aquatic invaders found that body size and prior residency generally mediate the outcome of aggressive encounters, but there is no consistent tradeoff between intra- and interspecific aggression. As the majority of studies on agonistic interactions focus on phylogenetically related species, I investigated such interactions between two unrelated invasive species that occupy a similar niche: the round goby (Neogobius melanostomus) and the spinycheek crayfish (Orconectes limosus), both benthic omnivores that compete for shelter. Laboratory experiments revealed that round gobies were more aggressive than crayfish, regardless of prior residency. Heightened aggression may be a selective advantage for an animal to invade a habitat occupied by another territorial species.
Les invasions d'espèces posent une menace à l'intégrité des communautés biologiques, puisque les espèces envahissantes peuvent gagner la compétition contre les espèces résidentes et en conséquence les supplanter. Le remplacement par des espèces envahissantes est souvent dû à leur comportement agressif. J'ai étudié ce phénomène en employant des méthodes de méta analyse et des expériences en laboratoire. Une méta analyse sur les actes d'agression chez les espèces envahissantes a démontré que la taille du corps et le statut de résidence antérieure affectent généralement le résultat des affrontements, mais il n'y a pas de compromis entre les actes d'agression intra et interspécifique. Puisque la plupart des études sur les interactions agonistes se concentrent sur des espèces apparentées taxonomiquement, j'ai examiné une telle interaction entre deux espèces envahissantes éloignées taxonomiquement qui occupent une niche semblable : le gobie à taches noires (Neogobius melanostomus) et l'écrevisse américaine (Orconectes limosus), deux omnivores qui se font compétition pour leur refuge. Les expériences en laboratoire ont démontré que les gobies à taches noires étaient plus agressifs que les écrevisses, indépendamment du statut de résidence antérieure. Le comportement agressif accru peut être un avantage sélectif qui permet à un animal d'envahir un habitat occupé par une autre espèce territoriale.

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Mahdavi-Arab, Nafiseh Verfasser], Wolfgang W. [Akademischer Betreuer] [Weisser, Johannes [Akademischer Betreuer] Kollmann, and Johannes [Akademischer Betreuer] Schnyder. "Plant invasion, insect herbivory and competition: insights into the ecological interactions between invasive goldenrod (Solidago canadensis) and native tansy (Tanacetum vulgare) / Nafiseh Mahdavi-Arab. Gutachter: Wolfgang W. Weisser ; Johannes Kollmann ; Johannes Schnyder. Betreuer: Wolfgang W. Weisser." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1062701208/34.

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Hunter, Dakota. "Invasive Species Research in Compensatory Wetland Mitigation: Investigating Plant Community Composition and Environmental Correlates with Three Invasive Plants." W&M ScholarWorks, 2019. https://scholarworks.wm.edu/etd/1563899036.

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Invasive plant species can alter natural communities and degrade ecosystem function, yet the factors influencing species invasion are poorly understood. Understanding how environmental factors affect plant invasion on compensatory wetland mitigation sites would allow wetland managers to approach invasive species management using a proactive approach (prior to invasion), thus minimizing the likelihood of invasive plants colonizing the system and degrading ecosystem function. In Chapter 1, I introduce the concepts and relevant literature used repeatedly in my project. In Chapter 2, I examine which key environmental factors are associated with altered plant community structure and invasive species prevalence on compensatory wetland mitigation sites. In Chapter 3, I look further into the plant community assemblage at each of my study sites and examine differences in the plant community at varying levels of invasive plant prevalence. For this study, Arthraxon hispidus (small carpet grass), Microstegium vimineum (Japanese stilt grass), and Typha spp. (cattail) were selected as representative invasive plants due to their abundance on non-tidal wetland mitigation sites, as well as their relative differences in ecological tolerance for environmental conditions (e.g., light availability or flooding). Within populations of these species, transects consisting of five 4m2 plots were established on 34 wetland mitigation sites within the Coastal Plain and Piedmont physiographic provinces in Virginia. Along transects, plots were randomly assigned to locations that captured the gradient from completely invaded (invasive species dominant) to uninvaded (invasive species absent or nearly so). For each plot, vegetation abundance data, soil samples, and canopy imagery were obtained for analysis. In Chapter 2, Canonical Correspondence Analysis (CCA) reveals iron, phosphorus, calcium, carbon:nitrogen ratio, canopy cover, and hydrology as correlates with variation in plant community composition across the invasion gradient. In Chapter 3, Spearman rank correlation results show no significant relationship between native species richness and invasive species abundance for any of the three species examined. Further analysis using Sørensen indices of similarity and species accumulation curves corroborate this result. Further study is required to determine causality in the relationships between invasive species and environmental variables, but results demonstrate the need for function-based criteria regarding invasive species management on compensatory wetland mitigation sites. Current standards encourage the use of non-specific herbicides, which may increase the risk of damaging native plant communities and perpetuating the cycle of disturbance and re-invasion on wetland mitigation sites.

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Johnston, Olivia Ruth. "Distribution and biology of the marine invasive bivalve Theora lubrica (Semelidae)." Thesis, University of Canterbury. School of Biological Sciences, 2005. http://hdl.handle.net/10092/2453.

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This study examined aspects of the biology and distribution of the marine invasive bivalve Theora lubrica in the Lyttelton Basin from two distinct sampling areas. Samples were collected monthly, over a 13 month period (January 2004 and January 2005), with particular emphasis on seasonal sedimentary characteristics and contamination. The sample sites consisted of five Port sites and five Harbour sites. They were sampled using a 20 litre anchor dredge. In winter and summer, core samples from each of the sample sites were collected, and the top 1.5cm of sediment was used to obtain sediment characteristics. Sediment characteristics indicated a depositional setting, with an average grain size (diameter) of 8-10 μm, which did not vary seasonally. Analysis indicated that the sediments naturally flocculated, to the 100μm size range and were platykurtic. Organic content (OC) in the sediment in Lyttelton Port showed significant seasonal variation. OC was highest during the winter period corresponding to an increase of T. lubrica abundance. There were noticeable seasonal changes in the abundance of T. lubrica, with high winter and low summer population densities. The period for recruitment coincided with high T. lubrica densities, and the greater frequency of juveniles with shell length below 4.33 mm. Histological sections showed that spawning occurred during the summer, confirmed by the presence of high percentages of ovigerous females and mature males. Community analyses distinguished four distinct seasonal and spatial benthic populations. The populations exhibited greater total species richness during the summer (compared to the winter). T. lubrica, maintained high abundance during periods of low total species richness. Furthermore, there was evidence of a predator prey relationship between the crab Macrophthalmus hirtipes and T. lubrica. Trace metals and hydrocarbons showed seasonal and spatial variation between the Port and Harbour sediments. Only the arsenic, nickel and copper in the Port location were at concentrations likely to be toxic to the biota. No trace metals exceeded threshold limits in the Harbour. Levels of arsenic and nickel were highest in the summer and copper was at its highest concentration in the winter. However, there was little evidence to suggest that the sediment contamination affects T. lubrica or the rest of the benthic community directly. Thus, the significantly lower species richness at the Port location may be due to other influences (i.e. sediment disturbance from shipping). In conclusion T lubrica is regarded as an opportunistic marine invasive species which can inhabit areas not occupied by other marine macro-biota. T lubrica did not appear to negatively impact the other benthic species at the Lyttelton Port or Harbour sites. It provided a plentiful food source and increased species diversity in sediments that are frequently disturbed (by shipping and wave action). Furthermore, T lubrica may help reestablish native species to the Port area by filtering and processing contaminated sediments (bioturbation), potentially pioneering the way for greater species diversity in Lyttelton Port and Harbour.

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Brueggemann, Angela Beth. "Exploring the population biology and invasive disease potential of Streptococcus pneumoniae." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400557.

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Wallquist, Elin. "Amphipod fauna of a mesotrophic lake – the distribution of the invasive amphipod, Echinogammarus ischnus." Thesis, Karlstad University, Faculty of Social and Life Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-566.

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In Oneida Lake, New York, USA, three species of amphipods are present: Hyalella azteca is native, Gammarus fasciatus is invasive and was first observed sometime before 1940 and Echinogammarus ischnus was introduced in 2001 in shallow water. The purpose of this study was to investigate the spatial and temporal abundance of amphipods in Oneida Lake. In the Great Lakes, the invasive E. ischnus has outcompeted G. fasciatus and this was also expected to be occur in Oneida Lake. Quantitative field sampling of transects that extended from the shore to deeper water (3.8 m) at six sites around Oneida Lake showed that the abundance of all amphipod species had a positive correlation to the abundance of zebra mussels (Dreissena polymorpha). Echinogammarus ischnus were observed at low densities (mean, 18 no./m2) in shallow water (<0.6 m) areas with cobbles covered with zebra mussels, whereas just a few individuals were found in deep water. At all depths, G. fasciatus were found at high densities (mean 950 no./m2), and H. azteca were present at low densities (mean 77 no./m2). The main factor limiting E. ischnus and its coexistence with G. fasciatus is the lack of favourable habitat i.e. too few cobble areas and too much Cladophora spp. and other macrophyte species growing in the lake. In addition, exposure of shallow water habitats every fall and winter as a consequence of water level manipulations produces unfavorable habitat for E. ischnus.

Sammanfattning

I sjön Oneida Lake, New York, USA, finns tre arter av märlkräftor (Amphipoda): Hyalella azteca är naturligt förekommande i sjön, Gammarus fasciatus hittades för första gången någon gång före år 1940 och Echinogammarus ischnus hittades för första gången 2001 på grunt vatten. Syftet med studien var att undersöka märlkräftornas utbredning och abundans över tid i Oneida Lake. I de Stora sjöarna (the Great Lakes) i Nordamerika har den invaderande E. ischnus konkurrerat ut G. fasciatus och samma sak förväntades att finna i Oneida Lake. I fält togs kvantitativa stickprover i transekter från strandlinjen och ut till djupt vatten (3,8 m), dessa visade att samtliga märlkräftsarter hade en positiv abundans korrelation med zebra musslor (Dreissena polymorpha). E. ischnus hittades i låga densiteter (medel 18 st/m2) på stenar täckta med zebra musslor på grunt vatten (<0,6 m) och endast ett fåtal individer hittades på djupt vatten. I Oneida Lake på alla djup hittades G. fasciatus i höga densiteter (medel 950 st/m2) medan H. azteca endast fanns i låga densiteter (medel 77 st/m2). Största anledningen till E. ischnus begränsning till samexistens med G. fasciatus är avsaknaden av gynnade habitat i sjön, det vill säga för få områden med stenar, samt att det växer för mycket alger (Cladophora spp.) och andra växter i sjön vilket missgynnar E. ischnus. Även vattennivåreglering under höst och vinter är ogynnsam för E. ischnus, då habitat på grunt vatten blir exponerande.

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Bertelsmeier, Cleo. "Biologie des invasions de fourmis dans un contexte de changement climatique." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112358/document.

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Le changement climatique et les invasions biologiques sont parmi les plus grandes menaces de la biodiversité et leurs impacts pourraient augmenter jusqu’à la fin du siècle. Parmi les espèces envahissantes, les fourmis sont un groupe particulièrement néfaste dû à leurs impacts sur les espèces natives, les processus écosystémique, la santé, l’agriculture et l’économie. L’objectif de cette thèse était de prédire les invasions de fourmis – en particulier avec le changement climatique qui pourrait favoriser les invasions en éliminant des barrières thermiques. J’ai utilisé trois approches complémentaires afin d’étudier le potentiel de différentes espèces à envahir : des modèles de distribution, des expériences comportementales et l’analyses d’une base de données de traits écologiques. J’ai modélisé l’aire favorable pour 15 espèces de fourmis parmi les pires, à la fois globalement, par continents, et dans les 34 hotspots de biodiversité. La distribution potentielle de seulement cinq espèce est prédite de diminuer (jusqu’à 35.8%) avec le changement climatique et l’aire potentielle diminue pour la plupart des espèces jusqu’à 63.2%. Les hotspots d’invasions de fourmis se situaient surtout dans des régions tropicales et subtropicales et ils correspondent particulièrement aux hotspots de biodiversité. Contrairement à ce qui est généralement admis, le changement climatique et les invasions biologiques n’agiront pas de manière synergique pour les fourmis. Par contre, les invasions de fourmis resteront probablement un problème global majeur, en particuliers dans les zones où les hotspots de biodiversité et les hotspots d’invasion se superposent. Les modèles de distribution ont identifié de larges zones de recouvrement entre aires favorables de plusieurs espèces de fourmis envahissantes. Dans le futur, ces espèces pourraient arriver simultanément dans les mêmes régions et entrer en compétition. Dans une série d’expériences, j’ai testé les différences comportementales entre 7 espèces de fourmis envahissantes (Anoplolepis gracilipes, Paratrechina longicornis, Myrmica rubra, Linepithema humile, Lasius neglectus, Wasmannia auropunctata et Pheidole megacephala). J’ai découvert deux stratégies comportementales différentes. Les interactions au niveau de la colonie ont suivi des processus démographiques plus complexes. De plus, j’ai mis au point deux expériences pour tester la capacité des fourmis envahissantes à explorer un nouvel espace et à exploiter des ressources. J’ai trouvé des différences significatives entre espèces et leur capacité à dominer par interférence comportementale était négativement corrélée à leurs capacités à découvrir et exploiter des ressources. Cette série d’expériences suggère que les ‘mécanismes’ d’invasion sont plus complexes que ce qui est généralement suggéré et que différentes espèces pourraient utiliser des stratégies comportementales différentes. Étant donné qu’il existe plus de 250 espèces de fourmis exotiques, il serait intéressant de pouvoir identifier à l’avance des futurs envahisseurs potentiels. Afin d’identifier des traits associés au caractère envahissant des fourmis, j’ai mis en place une base de données qui contient 2193 espèces de fourmis et 24 traits écologiques. J’ai effectué une analyse préliminaire de différences de traits entre fourmis natives et envahissantes qui a montré qu’il existe clairement des groupement distincts de natives et envahissantes, avec les espèces exotiques au milieu. Ces résultats pourraient servir de base pour construire un modèle prédictif des invasions de fourmis. Ces différentes approches (modèles, expériences, base de données) sont complémentaires car elles s’intéressent à des aspects différents du futur des invasions de fourmis qui sera vraisemblablement fortement influencé par le changement climatique. Le pires envahisseurs de demain ne seront probablement pas les même qu’aujourd’hui et les zones les plus à risque pourraient changer également
Climate change and biological invasions are both among the greatest threats to biodiversity and their impacts might increase by the end of the century. Among invasive species, ants are a prominent group due to their negative impacts on native species, ecosystem processes, human and animal health, agro-ecosystems and the economy. The objective of this thesis was to forecast future ant invasions – especially in the light of on-going climate change, which is generally thought to favour invasive species by removing thermal barriers. I used three complementary approaches to study the potential of different ant species to invade in the future: species distribution modelling, behavioural experiments and the analysis of a database of ecological traits. I modelled suitable area for 15 of the worst invasive ant species, both currently and with predicted climate change, globally, regionally and within the world’s 34 biodiversity hotspots. Surprisingly, the potential distribution of only five species was predicted to increase (up to 35.8%) with climate change, with most declining by up to 63.3%. The ant invasion hotspots are predominantly in tropical and subtropical regions of South America, Africa, Asia and Oceanic islands, and particularly correspond with biodiversity hotspots. Contrary to general expectations, climate change and biological invasions will not systematically act synergistically for ants. In addition, I found that the impacts of climate change can change over time and even reverse the trend of the impact (i.e., an increase instead of a decrease or vice versa). However, ant invasions will likely remain as a major global problem, especially where invasion hotspots coincide with biodiversity hotspots. The species distribution models have identified large potentially overlapping distributions of several invasive ants. In the future, these species may arrive simultaneously in the same regions and compete with each other. In a series of experiments, I tested behavioural differences among 7 highly invasive ant species (Anoplolepis gracilipes, Paratrechina longicornis, Myrmica rubra, Linepithema humile, Lasius neglectus, Wasmannia auropunctata and Pheidole megacephala). I discovered two different behavioural strategies among invasive ants. Interactions at the colony level, exhibited more complex demographic processes and more variability. Further, I investigated resource competition and differences in resource exploitation. I found significant differences among species, with competitive abilities that were negatively correlated with behavioural dominance. This series of experiments suggests that the ‘mechanisms’ of invasiveness are more complex than previously thought and that different invasive ant species may use different behavioural strategies. Since there are more than 250 exotic species of ants, it would be interesting to identify potential future invaders. In order to identify traits associated with invasiveness in ants, I set up a database with 2193 ant species and 24 ecological characteristics. I performed a preliminary analysis of trait differences between native and invasive ants that shows clearly different clusters of invasive and native species, with exotic species in between. These results could be used as a basis to construct a predictive model of future ant invasions. The different methods used (models, experiments, database) are complementary in that they explore different aspects of the future ant invasions which are likely to be influenced by on-going climate change. The worst invaders of tomorrow may not be the same as today and similarly, areas most at risk are likely to change

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Dandelot, Sophie. "Les Ludwigia spp. Invasives du Sud de la France : Historique, Biosystématique, Biologie et Ecologie." Aix-Marseille 3, 2004. http://www.theses.fr/2004AIX30052.

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Depuis leur introduction au début du XIXème siècle à Montpellier, les Ludwigia d’origine américaine ont, peu à peu, envahi toute la France. Notre étude morphologique et cytogénétique a permis de confirmer la présence en France de deux taxa bien différents. Les diploïdes (2n=16) correspondent à L. Peploides subsp. Montevidensis (Spreng. ) Raven, et les décaploïdes (2n = 80) à L. Grandiflora subsp. Hexapetala (Hook. & Arn. ) Nesom & Kartesz. Les diploïdes colonisent surtout la région méditerranéenne (sauf l’extrême Sud-Est), tandis que les polyploïdes prédominent partout ailleurs. De plus, ces deux taxons possèdent une intense multiplication végétative, mais des modes distincts de reproduction sexuée. Le second objectif de ce travail a été de comprendre quels sont les impacts des Ludwigia sur les écosystèmes. Nous avons suivi les relations entre le développement des herbiers de Ludwigia avec la qualité de l’eau, les autres producteurs primaires, les communautés bactériennes et la macrofaune. Pour cela, nous avons prospecté différents écosystèmes aquatiques méditerranéens caractérisés par des propriétés physiques et des fonctionnements hydrologiques différents
Since they were first introduced at the beginning of the 19th century into the Lez river at Montpellier, the American Ludwigia have gradually colonized the whole of France. A morphological and cytogenetic study confirmed the presence of two different taxa in France. The diploids (2n=16) correspond to L. Peploides subsp. Montevidensis (Spreng. ) Raven, and the decaploids (2n = 80) to L. Grandiflora subsp. Hexapetala (Hook. & Arn. ) Nesom & Kartesz. The diploids mainly colonize the Mediterranean region (except for the south-eastern part), while the polyploids predominate in all the other regions. Both taxa show an intense vegetative growth, but they have distinct breeding systems. The second objective of this study concerns the question of whether Ludwigia stands have an impact on ecosystems. We have study relations between Ludwigia growth and water quality, other primary producers, bacteria communities and macrofauna. We have investigated several mediterranean aquatic ecosystems mainly distinguished by their physical properties and their hydrological functioning

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Zumkier, Ulrich [Verfasser]. "Impacts of the invasive alien Heracleum mantegazzianum on native plant-pollinator interactions / Ulrich Zumkier. Fakultät für Biologie." Bielefeld : Universitätsbibliothek Bielefeld, Hochschulschriften, 2012. http://d-nb.info/1019892471/34.

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Almqvist, Gustaf. "Round goby Neogobius melanostomus in the Baltic Sea : invasion biology in practice /." Stockholm : Department of Systems Ecology, Stockholm University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7450.

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Trexler, Christina M. "Biology, ecology and control of the invasive channeled apple snail, Pomacea canaliculata." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5062.

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Invasive species are detrimental to native biotas worldwide. Recently, Florida was invaded by a freshwater snail (Pomacea canaliculata) native to Argentina. This snail is a serious pest of rice crops in Asia, but little is known about its interactions within Florida ecosystems. Possible competitive exclusion of the native congener (P. paludosa) is a concern because it is the almost exclusive prey of the federally endangered Everglades snail kite (Rostrhamus sociabilis). My research consisted of three parts. First, to identify possible methods to control P. canaliculata in the egg stage, I experimentally evaluated the effects of photoperiod, substrate availability, and food type and availability on hatching success and hatchling survival. None of these factors significantly affected hatching or survival, suggesting that P. canaliculata could invade many water bodies. Second, I used a randomized block design to assess the separate and combined effects of population density and food availability on growth and spawning of P. canaliculata. Food availability but not density significantly affected growth; snails fed less food grew less, but neither factor affected spawning. Third, I used a replacement series design to assess competition between P. canaliculata and P. paludosa under food limitation. For both species, snails fed less grew significantly less, and snails exposed to greater congener densities spawned less than when exposed to conspecifics only. While my results predict that P. paludosa should exclude P. canaliculata, previous literature and current invasions suggest that the exotic snail may co-exist with its North American congener.
ID: 030422795; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2011.; Includes bibliographical references (p. 53-63).
M.S.
Masters
Biology
Sciences

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Courant, Julien. "Invasive biology of Xenopus laevis in Europe : ecological effects and physiological adaptations." Thesis, Paris, Muséum national d'histoire naturelle, 2017. http://www.theses.fr/2017MNHN0024/document.

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A cause de l’actuel déclin mondial de la biodiversité, la compréhension des conséquences de chaque menace sur la biodiversité est un élément crucial en biologie de la conservation. Les espèces exotiques envahissantes représentent une de ces menaces à l’échelle mondiale, et peuvent induire localement des dommages au sein des écosystèmes. Etudier les phénomènes régissant les effets négatifs de ces espèces, et leurs potentiels d’expansion apparaît actuellement comme un élément crucial pour déterminer leurs effets sur le long terme. Dans cette étude, nous focalisons nos efforts sur une population exotique envahissante du Xénope lisse, Xenopus laevis, en France, pour apporter de nouvelles connaissances sur les interactions de cette population avec son environnement et pour étudier les changement dans l’allocation des ressources aux traits d’histoire de vie liés à la reproduction la survie et la dispersion durant l’expansion de l’aire de répartition. Nous étudions le régime alimentaire de l’espèce en France et dans d’autres populations introduites et autochtones et concluons que cette espèce peut étendre sa répartition en consommer une faible, comme une importante diversité de proies. Nous détectons également un potentiel impact de l’espèce sur les amphibiens autochtones de France. Dans la seconde section de la thèse, nous rapportons une réduction de l’allocation des ressources à la reproduction et une augmentation de la dispersion, sur le front de colonisation. Enfin, nous étudions la dynamique des populations et détectons une faible probabilité de survie, et une faible densité en individus dans le centre de l’aire de répartition. La combinaison de ces résultats suggère que les potentiels effets négatifs sur le long terme sont importants pour cette espèce, en France, tout comme dans d’autres zones où l’espèce a été, ou sera, introduite
Because of the current global biodiversity decline, understanding the consequences of each threat on biodiversity is crucial for conservation biology. Invasive species are among the main threats at the global scale, and can locally imply harmful damages on ecosystems. Studying the phenomena driving the effects and potential for expansion of these species appears as a crucial element to assess their long terms impacts. In this study, we focused our efforts on an invasive population of the African clawed frog, Xenopus laevis, in France, to bring insight about the interactions of this population with its environment and to study the changes in resource allocation to the life history traits, related to reproduction, survival and dispersal probabilities, during the range expansion of the population. We studied the diet in the French invasive population and in other invasive and native populations, and found that this species can expand by predating a narrow, as well as a broad, range of prey categories. We also detected an impact of X. laevis on the native amphibian community in France. In the second section of the thesis, we reported a decrease in reproductive investment, and an increased dispersal allocation of resources at the range edge. We finally studied population dynamics and detected a lower survival probability and density at the range core. All these results combined suggest that the potential for long term impacts is important in France for X. laevis as well as in other areas where the species has been, or will be, introduced

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Rowekamp, Erin Catherine. "Seeing the Forest and the Stream: Assessing the Influence of Riparian Invasion by the Exotic Shrub Amur Honeysuckle (Lonicera maackii) on Terrestrial-to-Aquatic Linkages." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1511907835465838.

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Palik, Destiny J. "The Invasive Potential of Perennial Biofuel Crops." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503309520467401.

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Thouvenot, Lise. "Stratégies de réponse de l'espèce invasive Ludwigia grandiflora aux contraintes environnementales." Rennes 1, 2012. http://www.theses.fr/2012REN1S141.

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Le succès des espèces invasives est influencé à la fois par les caractéristiques de l’espèce exotique et les caractéristiques de la communauté d’accueil. Il va donc dépendre des stratégies de réponses de ces espèces aux contraintes environnementales. Dans cette thèse, nous nous sommes intéressés à une espèce végétale : l’espèce Ludwigia grandiflora subsp. Hexapetala, la Jussie à grandes fleurs. Cette espèce amphiphyte est considérée comme la plante « aquatique » la plus invasive en France. Cette thèse vise à approfondir nos connaissances sur les mécanismes d’adaptation, les stratégies de croissance et de colonisation de cette espèce face aux contraintes environnementales afin de mieux comprendre et expliquer son succès invasif. Les réponses de cette espèce face à des paramètres abiotiques et biotiques ont été étudiées via une approche par les traits fonctionnels. Pour cela, des approches expérimentales en conditions contrôlées et semi-contrôlées ont été réalisées. Nos résultats montrent que cette espèce possède une grande capacité d’adaptation aux fluctuations des paramètres abiotiques du milieu. Par ailleurs, L. Grandiflora possède un taux croissance élevé, elle est capable de compenser la perte de biomasse due à la pression des herbivores et forme une dense canopée en réponse à la compétition. La stratégie de réponse de L. Grandiflora aux pressions biotiques est à la fois dépendante de sa propre densité, de la densité et du statut de l’espèce voisine (indigène vs exotique), mais aussi du milieu (terrestre vs aquatique). Les stratégies de réponses de cette espèce face aux contraintes abiotiques et aux interactions biotiques pourraient expliquer son succès invasif
The success of invasive species depends on the characteristics of exotic species (their biological traits) and the characteristics of their introduced habitats (biotic and abiotic characteristics). The success of these species will depend on their response strategies to environmental constraints. In this thesis, we focus on the the Large Water Primrose plant species, Ludwigia grandiflora subsp. Hexapetala,. This amphiphyte species is considered as the most invasive aquatic plant in France. The present thesis aims to improve our knowledge on the adaptive strategies of Ludwigia grandiflora to environmental constraints in order to better understand and explain its invasive success. The responses of this species to abiotic parameters and biotic interaction were investigated using a functional traits approach. To achieve these goals, we conducted microcosm and mesocosm experiments. We demonstrated that L. Grandiflora possesses a large adaptive capacity to respond to fluctuations of abiotic factors (e. G. Variation of water depth, light intensity, salinization of ecosystems). Furthermore, our results showed that L. Grandiflora had a high growth rate, compensated herbivore damages and was able to produce a dense canopy in response to competition. However, the response strategy of L. Grandiflora to biotic pressure (competition and predation) depended on its own density, on the density and the status (native vs exotic) of neighboring species and on its environment (terrestrial vs aquatic). The response strategies of L. Grandiflora face to abiotic parameters and biotic pressure could explain its invasive success

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Correa-Guzman, Cristián. "Ecological impacts of invasive trout in Patagonian lakes." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110451.

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Earth is undergoing an acute anthropogenic biodiversity crisis, and invasive species are a primary cause. Understanding the ecological impacts of two of the most disruptive cosmopolitan freshwater fish invaders, brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss), is a priority to develop conservation guidelines and learn about the functioning of natural ecosystems. The impacts of these salmonids native to the northern hemisphere are especially worrisome in cold-temperate freshwaters of the Southern Hemisphere, where they are now popular as sport fish. This region is the realm of the Galaxiidae, a family of freshwater and diadromous fishes considered amongst the most seriously threatened fishes known. The decline of galaxiids has been linked to trout invasions but data is often qualitative and ambiguous. Furthermore, little is known about the extent to which native ecosystems have been transformed, especially in lakes. My goal is to remedy some of these deficiencies by investigating Patagonian lakes. In order to isolate the impacts of trout on a single galaxiid species I chose an especially fish-depauperated study system – 25 lakes with only galaxiids and/or trout. Results of fishing catch-per-unit-effort data showed a strong negative association between the density of trout and the density of the most widespread Patagonia-endemic galaxiid, Galaxias platei. Furthermore, I ruled out alternative natural and anthropogenic confounding effects, and identified a critical natural constraint to salmonid invasion success which is widely applicable. Given the strong population-level impacts on the native fish, I examined the possibility of food web disruptions by focusing on isotopic (δ15C and δ13N) ontogenetic niche shifts. I looked at the reciprocal effects of the native and the invasive fish density on each other, a perspective rarely studied. I found strong effects whereby the galaxiid lost, at high trout density, its ability to enhance its trophic position during ontogeny, while trout achieved a high trophic position only at high G. platei density. Finally, by studying zooplankton along the galaxiid-trout density countergradient, I could demonstrate both a negative, strong top-down control on zooplankton elicited solely by G. platei, and a positive, strong top-down control elicited by the cascading effects of trout. My dissertation delivers overdue evidence of the detrimental effects of invasive trout on Patagonian galaxiids, contributes to the understanding of salmonid invasion ecology, and provides several mechanistic hypotheses and new perspectives on the pervasive nature of the ecological impacts of invasive fish predators. Based on my results, I advocate the management strategy of culling trout from overpopulated lakes to simultaneously protect native fish and enhance a lucrative sport fishery for large trout, and encourage the active protection of rare relicts of unspoiled native biodiversity.
La biodiversité est confrontée à une crise sans précédent de transformations d'origine anthropique causée principalement par l'introduction d'espèces invasives. Au niveau des écosystèmes aquatiques d'eau douce, la compréhension des impacts écologiques engendrés par l'introduction de poissons prédateurs agressifs tels que les truites brunes (Salmo trutta) et les truites arc-en-ciel (Oncorhynchus mykiss) est une priorité pour le développement de lignes directrices en conservation. L'étude des changements causés par ces espèces fournit également l'opportunité de mieux comprendre les écosystèmes naturels. L'impact de ces salmonidaes natifs de l'hémisphère nord et maintenant populaires dans le domaine de la pêche sportive dans les écosystèmes tempérés de l'hémisphère sud est une préoccupation particulière. Cette région est également le domaine des galaxiidae, famille de poissons amphihalins natifs de cette région, qui sont sérieusement menacés. Le déclin des galaxiids est souvent lié à l'invasion des truites, mais les données à ce sujet sont souvent qualitatives et ambiguës. De plus, peu d'information est connue concernant le niveau de transformation des écosystèmes natifs, particulièrement dans les écosystèmes lacustres. Mon objectif est de remédier à ces lacunes en étudiant les lacs en Patagonie. Dans le but d'isoler l'impact de l'introduction des truites sur une espèce spécifique de galaxiids, j'ai choisi un système d'étude composé de 25 lacs, dont certains sont peuplés de galaxiids seulement, et d'autres de galaxiids et de truites. Les données capture-par-unité-d'effort ont démontré une forte relation négative entre la densité des truites et l'espèce la plus répandue de galaxiids endémiques en Patagonie, Galaxias platei. De plus, j'ai séparé les effets naturels des effets anthropogéniques, et j'ai identifié une contrainte naturelle critique très répandue pour le succès de l'invasion des espèces salmonidés. Étant donné le fort impact observé au niveau des populations sur les poissons natifs, j'ai également étudié les perturbations sur la composition de la chaîne alimentaire en examinant les changements isotopiques (δ15C and δ13N) de la niche ontogénétique. J'ai étudié les effets réciproques entre la densité des poissons natifs et la densité des poissons invasifs, une perspective rarement étudiée. J'ai observé qu'à de hautes densités de truites, les galaxiids on perdu leur habilité d'augmenter leur position trophique durant leur ontogénie, alors que les truites obtiennent une haute position trophique seulement en présence d'une haute densité de G. platei. Finalement, en étudiant la communauté de zooplankton dans un gradient de densité de populations de truites et de galaxiids, j'ai démontré un fort effet négatif de contrôle par le haut sur le zooplankton causé seulement par G. platei, et un fort effet positif de contrôle par le haut causé par un effet de cascade induit par la présence de truites. Ma dissertation fournit une preuve longuement attendue des effets nuisibles des truites introduites en Patagonie sur les galaxiids, contribue à la compréhension de l'écologie de l'invasion des salmonidés, et propose plusieurs hypothèses méchanistiques ainsi que de nouvelles perspectives sur la nature envahissante des impacts écologiques de l'introduction des poissons prédateurs. En fonction de mes résultats, je supporte la stratégie de gestion de retirer les truites des lacs surpeuplés pour protéger à la fois les populations de poissons natifs, pour améliorer l'efficacité de la pêche sportive pour de grosses truites, et pour encourager une protection active des dernières reliques intactes de la biodiversité.

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Perdereau, Elfie. "Biologie de l'invasion d'un termite américain en France : évolution de l'organisation sociale et conséquences sur le succès invasif." Thesis, Tours, 2010. http://www.theses.fr/2010TOUR4024/document.

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L’augmentation des problèmes liés aux invasions biologiques nécessite une meilleure compréhension des mécanismes permettant le succès invasif d’une espèce. Chez les insectes sociaux invasifs, les études se sont focalisées sur les Hyménoptères, et ont montré que l’organisation sociale des populations introduites présentait des caractères propres. L’objectif principal de cette thèse est de caractériser l’organisation sociale des populations introduites chez les termites (Isoptères) à travers l’étude de l’invasion de Reticulitermes flavipes en France. L’ensemble des résultats révèle que (i) l’organisation sociale des populations introduites varie de celle des populations natives en présentant une forme extrême de néoténie et une forte capacité à fusionner ; (ii) ces variations semblent résulter d’une évolution suite à l’introduction et (iii) avoir favorisé l’installation et l’expansion de ce termite en France, similairement à l’unicolonialité et la polygynie des Hyménoptères sociaux introduits. Les possibles origines évolutives des variations observées entre les populations natives et introduites de R. flavipes sont discutées
The increasing of ecological and economical problems linked to biological invasion phenomenon necessitate a better understanding of mechanisms allowing an invasive success. In social insects, studies are mainly focused on social Hymenoptera, and has demonstrated that social organization of introduced populations presented particular characters allowing their invasive success. The principal objective of my PhD is to characterize the social organization of the introduced populations in Isoptera through the study of the American termite Reticulitermes flavipes introduced in France. The overall of results reveals (i) strong variations of social organization between native and introduced populations presenting a extreme form of neoteny and a strong capacity to colonial fusion; (ii) these variations seem to have evolved after its introduction in France, and (iii) to allow the establishment and expansion of R. flavipes in France, similarly to unicoloniality and polygyny observed in the social invasive Hymenoptera. The possible evolutionary origins of the observed variations between native and introduced populations of R. flavipes are discussed

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Cook, Cassandra. "Impacts of Invasive Phragmites Australis on Diamondback Terrapin Nesting." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477068338.

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The diamondback terrapin (Malaclemys terrapin) is a species of turtle found exclusively in brackish water habitats. Terrapins are currently facing population threats including by-catch mortality in crab pots, predation, and habitat loss. The expansion of the exotic, invasive reed Phragmites australis is causing widespread structural and functional changes to coastal ecosystems throughout North America, which could negatively impact the nesting success of female terrapins by invading preferred nesting habitats. I examined the extent to which Phragmites affects nesting of a breeding population of diamondback terrapins at Fisherman Island National Wildlife Refuge on the eastern shore of Virginia, where Phragmites has recently expanded into known areas of terrapin nesting. With data collected from the 2015 nesting season I quantified the impacts of this expansion on terrapin nesting by: determining the extent to which nest incubation temperature is impacted by Phragmites shading, determining how Phragmites density impacts the risk of rhizome invasion into nests, and determining how the presence of Phragmites impacts predation of terrapin nests. I also examined landscape features to determine which factors may be associated with diamondback terrapin nest site use. I found that Phragmites cover greater than 50% would decrease incubation temperatures of terrapin nests sufficiently to produce predominantly male hatchlings. There was no effect of Phragmites cover on root growth into simulated nests, but cover by other dune plant species explained observed trends in root growth. I did not find a significant effect of Phragmites on nest predator activity, but did find that Phragmites had an impact on terrapin nest site use on Fisherman Island. Distance from nest to nearest marsh and tidal creek also influenced terrapin nest site use. With crab pots and roadways contributing to high adult mortality every year, high nesting success will be highly important to maintaining and propagating this charismatic species.

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Lombaert, Eric. "Biologie évolutive d'une espèce envahissante, la coccinelle asiatique Harmonia axyridis." Electronic Thesis or Diss., Montpellier 2, 2011. http://www.theses.fr/2011MON20248.

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Les invasions biologiques constituent aujourd'hui une source d'inquiétude du fait de leur nette augmentation et des conséquences écologiques, économiques et sanitaires dont elles sont à l'origine. Pour qu'une population devienne envahissante, il faut (i) qu'elle soit introduite, (ii) qu'elle s'établisse et (iii) qu'elle prolifère. Chacune de ces trois étapes constitue un défi difficile à relever, et les processus en jeu sont encore mal connus. Cette thèse décrit un ensemble de recherches visant à comprendre l'invasion mondiale particulièrement réussie de la coccinelle asiatique Harmonia axyridis. Nous avons dans un premier temps étudié l'étape d'introduction en retraçant les routes d'invasion d'H. axyridis à l'aide de marqueurs microsatellites et de la méthode ABC (Approximate Bayesian Computation). Nous avons montré que la population envahissante la plus ancienne dans le nord-est américain avait été la tête de pont de l'invasion mondiale en devenant la source des foyers européen, sud-américain et africain. En Europe, on constate également une hybridation avec une souche de lutte biologique. Dans un deuxième temps, nous avons exploré l'étape d'établissement de l'espèce. Nous avons montré que les populations envahissantes d'H. axyridis avaient subi une purge génétique réduisant considérablement les effets associés à la dépression de consanguinité. Par ailleurs, l'événement d'hybridation en Europe apporte des avantages phénotypiques probables à cette population envahissante. Nous avons ensuite étudié plusieurs aspects de l'étape de prolifération. Nous avons montré que les populations européennes avaient évolué vers de plus fortes capacités de dispersion sur le front d'invasion. Par ailleurs, nos résultats montrent que la commercialisation en France d'une souche non-volante de lutte biologique a pu avoir des conséquences positives sur l'expansion de la population envahissante par des phénomènes d'hétérosis ou d'augmentation de variance génétique. Enfin, nous discutons de l'importance d'étudier de manière approfondie une espèce modèle telle qu'H. axyridis pour améliorer nos connaissances générales sur les mécanismes éco-évolutifs impliqués lors des invasions biologiques
Biological invasions are a concern because of their increase and their environmental, economic and human health consequences. To become invasive, a population must (i) be introduced, (ii) established itself and (iii) proliferates. Each of these three steps constitutes a challenge, and the processes involved are still poorly understood. This thesis describes a set of research actions which aims at understanding the worldwide successful invasion of the Asian ladybird Harmonia axyridis.We first investigated the introduction step by retracing invasion routes of H. axyridis using microsatellite markers and the ABC (Approximate Bayesian Computation) method. We have shown that the oldest invasive population in the eastern North America acted as a bridgehead of the worldwide invasion by becoming the source of the European, the South American and the African outbreaks. We also found evidence for a genetic admixture event in Europe with a biological control strain.Second, we explored the establishment step. We have shown that invasive populations of H. axyridis endured a genetic purge which significantly reduced adverse effects associated with inbreeding depression. In addition, the admixture event in Europe likely brought phenotypic benefits to this invasive population.We then studied several aspects of the proliferation step. We found that European populations had evolved towards higher dispersal abilities on the invasion front. Moreover, our results show that the use of a flightless biocontrol strain which is still sold in France may have a positive impact on the expansion of the invasive population through heterosis or increased of genetic variance.Finally, we discuss the importance of studying in detail a model species such as H. axyridis to improve our general understanding of the eco-evolutionary mechanisms involved in biological invasions

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Coon, Courtney A. c. "Host-Parasite Interactions in an Invasive Songbird." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5004.

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Introduced species are the greatest threat to biodiversity after habitat loss. Understanding the processes that permit organisms to become successful invaders may provide opportunities to prevent or limit their dispersal and establishment and thereby alleviate some of their harmful effects. The goal of my dissertation research has been to investigate whether invasive species have distinctive interactions with parasites, and some of the mechanisms that may underlie that variation. I used one of the world's most successful vertebrate invaders as a case study: the house sparrow (Passer domesticus; Introduction). Previous research in the house sparrow suggested that loss of parasite diversity may contribute to invasion success. However, my work demonstrates that infection with common avian malaria parasites is primarily a function of environmental heterogeneity and is not a predictor of time since introduction for house sparrows that are currently expanding their range in Kenya (Chapter 1). Interestingly, in spite of a large proportion of the population being infected with avian malaria, a state that should reduce competitive ability of house sparrow populations, this species is still able to establish themselves among native competitors. Though there are a number of potential mechanisms that could explain this pattern, one of the most convincing explanations is that house sparrows, and perhaps other introduced species, have adaptive differences in immunity. As such, the findings of Chapter 1 inspired two studies in which my collaborators and I showed that house sparrows from two non-native populations seem capable of maintaining normal health, performance and behavior during immune challenge, a response often referred to as parasite tolerance. Specifically, in Chapter 2, we found that when Floridian house sparrows, established since ~1870, were challenged with synthetic pathogens that mimicked infection with a fungi, an RNA virus or Gram-negative bacteria, only individuals challenged by the synthetic bacteria showed measurable sickness behaviors and secretion of an inflammatory protein. In Chapter 3, we compared parasite tolerance in Kenyan house sparrows (introduced in ~2000) and a native congener, the grey-headed sparrow (P. griseus) to a common intestinal parasite of songbirds. We found that both species were tolerant in that they were able to maintain fat reserves, protein reserves and vertical flight ability during infection. However, house sparrows maintained burdens that were, on average, more than 10x those of grey-headed sparrows. Moreover, when examining nutrient allocation in the two species, house sparrows appeared to assimilate nutrients more efficiently than grey-headed sparrows and did not change how nutrients were allocated among immune and reproductive organs during experimental infection. Grey-headed sparrows, however, did shift nutrient allocation among immune and reproductive organs during experimental infection. Together, the larger nutrient pool and maintenance of nutrient allocation patterns in challenged house sparrows suggests that no physiological trade-offs occurred and that house sparrows experienced a lower cost of parasite exposure. In the fourth Chapter, I explored why house sparrows had such high coccidia burdens in comparison to their congeners. We suspected burden was a function of the frequency of exposure to coccidia. Consequently, we explored heterogeneity in foraging preferences and other behaviors in Floridian house sparrows and their role in coccidia burden. As expected, we found that house sparrows did not avoid contaminated food. In fact, they ate contaminated and uncontaminated foods indiscriminately. What was surprising was a lack of correlation between burden and consumption of contaminated foods and all of the behaviors we monitored (i.e., aggression, activity, feeding rates and defecation frequency). Overall, these data suggest that house sparrows do not benefit from typical parasite-avoidance behaviors. In sum, this dissertation research implies that house sparrows respond to parasite infection differently than many other known vertebrates, most likely in an effort to maximize efficient use of resources and, in so doing, augment competitive ability and invasion success.

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Mirsa, Berivan. "Parkslide, från prydnad till invasiv." Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-21484.

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Enligt ArtDatabanken (2020) är parkslide en invasiv främmande art i den svenska naturensom hotar den biologiska mångfalden lokalt i södra och mellersta delen av landet. I studienges genom litteraturöversikt och semistrukturerade intervju en större förståelse kringparkslides egenskaper, tillväxt, etablering, spridning, inverkan på omgivningen, metoder somanvänds för att bekämpa den och vad som kan komma att bli framtida utmaningar.Empirin har analyserats utifrån evolutionsteori, termen ekologi och begreppet globalisering.Slutsatsen visar att parkslide är en extrem och svårbekämpad invasiv art som hotar andra arteri sin omgivning. Den påverkar strukturer samt orsakar stora ekonomiska kostnader församhället. Slutsatsen visar också att än idag finns det ingen metod som kan utrota parkslidehelt. I framtiden kommer det behövas nya lagstiftningar om parkslide till följd av attproblemet blir värre i takt med ökad klimatförändringar och befolkningstillväxt.
According to ArtDatabanken (2020), the Reynoutria japonica is an alien invasive species inSwedishs nature that threatens the local biodiversity and especially in the south and middlepart of Sweden. In this study I have through litterature review and interviews, created ancomprehension about Reynoutria japonica’s capacities, life cycle, environment,establishment, dissemination, impact on the environment, methods that are used to combat theplant and what could be future challenges with Reynoutria japonica. The empirical have beenanalyzed with evolutionary theory, the term ecology and the concept of globalization. Myconclusions show that Reynoutria japonica is an extremely difficult invasive species tocombat and it threatens other species in the environment. Reynoutia japonica affectsstructures and causes financial costs for the society. My conclusions also show that untiltoday there is no method that can completely eradicate Reynoutria japonica. In the futurethere will be need for new new legislation about Reynoutria japonica due to the problemgetting worse with increased climate change and population growth.

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Pontes, Fênix Porto. "Biologia da invasão de Hemidactylus mabouia no Brasil : análise da estrutura genética populacional." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/24294.

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Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-Graduação em Zoologia, 2017.
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Espécies invasoras vêm tendo um crescente interesse nos últimos anos. Seja pelos impactos econômicos ou pelos seus impactos ecológicos, eventos de invasão de espécies proporcionam oportunidades de estudo interessantes dentro das áreas de genética de populações e evolução. Hemidactylus mabouia é uma espécie de geconídeo com alta capacidade invasora. Atualmente é encontrada em quase todo o Brasil e tem na literatura um suporte estabelecido de invasão do continente Americano por meio de auxílio antrópico. Estudos feitos com essa espécie encontraram um padrão de estruturação genética progressiva durante o processo de invasão da espécie dentro da Flórida (EUA), onde o número de agrupamentos crescia conforme a diversidade genética abaixava, enquanto a espécie adentrava mais para o interior daquele estado. O presente estudo avalia a estruturação e a diversidade genética da H. mabouia no Brasil. Foram comparados a diversidade e os perfis genéticos usando marcadores de microssatélites de populações em regiões de invasão primária e invasão secundária. Os resultados encontrados diferem dos encontrados na Flórida. Porém, os resultados encontrados sugerem que a espécie está bem disseminada no Brasil com a caracterização de dois grupos (sem diferença significativa de diversidade). Esses grupos podem ter suas formações associadas de maneira bem próxima às atividades econômicas humanas.
Invasive species have been getting a growing interest in the last years. Whether by their economic or their ecological impacts, invasive species events generate interesting study opportunities inside the population genetics and evolution fields. Hemidactylus mabouia is a gecko species with a high invasive potential, currently it has been found in almost all Brazil’s territory and has in the literature an established support of invasion aided by human intervention in the American continent. Studies made with this species have found a pattern of increasing genetic structuration during its invasion process in the Florida state (USA), where the number of clusters increases while the genetic variability went down at the same time that the species went into Florida’s interior. The present study evaluates the genetic structure and diversity of H. mabouia in the Brazil. The genetic populational clusters and genetic diversity were compared using microsatellites markers of populations from primary invasion regions and secondary invasion regions. The results found differ with those found in Florida. The results, however, suggest that the species is well-distributed in Brazil, with the formation of two groups (with no significative difference in genetic diversity between them). These groups may have their formation origins associated in close manner with human economic activities.

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Banerjee, A. K. "The detection, outcome and molecular biology of pre-invasive lesions of the bronchus." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1343628/.

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Introduction: It is proposed that squamous cell carcinoma of the bronchus develops from carcinogen-exposed epithelium through a series of pre-invasive lesions of increasing histological and cytological abnormality. This has not been reliably demonstrated, and it is not known whether pre-invasive lesion development follows a predictable time-course and pattern or whether all pre-invasive lesions are committed to the development of malignancy. Pre-invasive lesions manifest genetic changes similar in pattern to that of squamous cell carcinoma. The accumulation of genetic damage, as a consequence of prolonged carcinogen exposure, may drive the progression of an individual pre-invasive lesion to malignancy, and the ultimate pattern of genetic changes may determine the outcome of that lesion. Methods: In the present work patients with pre-invasive lesions underwent serial bronchoscopy and biopsy to determine the natural history of pre-invasive lesions. Serial biopsies from lesions under follow-up were studied histologically and using loss of heterozygosity analysis at chromosomal loci thought to be involved in the pathogenesis of squamous cell carcinoma. Results: The natural history of pre-invasive lesions is variable. Some lesions progress, some regress and some remain unchanged histologically. Different lesions in a single patient may have different natural histories and different outcomes. Short-term follow-up may misrepresent the long-term evolution of an individual lesion or bronchoscopic location. Molecular studies showed that different lesions in individual patients appeared to have originated from a single progenitor cell, but acquired significant genetic differences during lesion development. Progression of pre-invasive lesions to carcinoma was associated with loss of heterozygosity along the majority of 3p with loss at 9p and the acquisition of 4p16 loss at the transition from carcinoma-in-situ to invasive disease. Regression to normal epithelium was associated with the failure to acquire these changes at the same time.

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Hammann, Sven [Verfasser]. "Invasion Biology of Mnemiopsis leidyi and its symbionts / Sven Hammann." Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1029293422/34.

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Enders, Martin [Verfasser]. "Creating and evaluating hypothesis networks in invasion biology / Martin Enders." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1205314857/34.

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Liebich, Viola [Verfasser], and Justus van [Akademischer Betreuer] Beusekom. "Invasive plankton : Implications of and for ballast water management / Viola Liebich. Betreuer: Justus van Beusekom." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1036729524/34.

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Haun, Florian [Verfasser], and Christoph [Akademischer Betreuer] Borner. "Signaling cascades of the Aspergillus fumigatus virulence factor Gliotoxin in mediating apoptosis and invasive aspergillosis." Freiburg : Universität, 2016. http://d-nb.info/1147680612/34.

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Lillian, Sarah. "Associational Susceptibility of a Native Shrub, Atriplex canescens, Mediated by an Invasive Annual Forb, Brassica tournefortii, and Invasive Stinkbug, Bagrada hilaris." Thesis, University of California, Riverside, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10624437.

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Indirect interactions have increasingly been recognized as important forces influencing population dynamics and structuring communities. Associational susceptibility is a form of indirect effect in which a focal plant experiences greater herbivore damage due to neighboring plant identity or diversity. These interactions remain poorly understood in the context of invasion ecology, though they may be responsible for huge impacts of invasive species on native communities. This dissertation investigates the potential mechanisms and consequences of associational susceptibility of a native perennial shrub, Atriplex canescens, driven by an invasive annual forb, Brassica tournefortii, and an invasive herbivorous stinkbug, Bagrada hilaris. In Chapter 1, a potential associational effect is experimentally demonstrated and a phenologically-driven trait is identified as a potential mechanism for this interaction. In Chapter 2, relative host plant quality is explored for its role in mediating the numerical response of the shared herbivore, and the herbivore’s damage impact on A. canescens. In Chapter 3, neighbor density, herbivore presence and herbivore density were manipulated to identify their impacts on spillover timing, extent, and fitness consequences for A. canescens. Overall, potential mechanisms of A. canescens associational susceptibility to Br. tournefortii and Ba. hilaris identified include: Ba. hilaris accumulation on Br. tournefortii followed by Br. tournefortii senescence and depletion, triggering Ba. hilaris alternative host-seeking. Associational susceptibility of A. canescens could not be re-created under experimental conditions, but further study is required to ascertain whether this interaction is due to experimental limitations or ecological implausibility.

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Matos, Sónia Maria Gomes. "Biologia e plantas hospedeiras de uma nova espécie galícola de eucaliptos em Portugal - Ophelimus SP." Master's thesis, ISA/UL, 2014. http://hdl.handle.net/10400.5/8285.

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Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia
In 2013, a new Ophelimus sp. was detected in a Eucalyptus arboretum in Lisbon. This study aims to study the bio-ecological characteristics of Ophelimus sp. as basic knowledge for its management. We further compare it with the previous introduced species Ophelimus maskelli. Our results showed morphological differences on the galls and adults of O. maskelli and Ophelimus sp., and on the host species. Eucalyptus globulus and E. viminalis were the most susceptible species to Ophelimus sp., whereas it was confirmed a preference of O. maskelli for E. camaldulensis, E. rudis and E. tereticornis. Intraspecific differences regarding gall size and infestation levels of Ophelimus sp. within E. globulus were further registered. Ophelimus sp. has one generation per year and about 30% of larvae and pre-adult mortality was registered due to unknown factors. These traits will contribute to a slower growth rate of its populations when compared to those of O. maskelli. In the North of Portugal, Ophelimus sp. seems to be better adapted, as indicated by the higher population levels compared to those observed in the South. From our surveys, we did not find galls with Closterocerus chamaeleon or any other parasitoid that could allow for the biocontrol of Ophelimus sp.

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Bifolchi, Aline. "Biologie et génétique des populations d'une espèce invasive : le cas du vison d'Amérique (mustela vison Schreber, 1777) en Bretagne." Phd thesis, Université d'Angers, 2007. http://tel.archives-ouvertes.fr/tel-00346327.

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Les invasions biologiques représentent la deuxième cause de perte de la biodiversité et participent aux changements environnementaux globaux. Parmi les espèces exotiques présentes sur le continent européen, le Vison d'Amérique (Mustela vison) a été introduit dans les années 1920 pour l'élevage pelletier. Des individus échappés d'élevage ou délibérément relâchés ont fondé des populations férales dans divers pays européens, représentant une sérieuse menace pour la faune autochtone. L'objectif de cette thèse est d'appréhender le fonctionnement de la population férale de Vison d'Amérique installée en Bretagne. Dans un premier temps, nous nous sommes intéressés à la répartition, aux densités de population ainsi qu'aux paramètres démographiques de la population. Nous avons déterminé que la population férale de Vison d'Amérique en Bretagne manifeste toutes les caractéristiques d'une espèce invasive. Une étude expérimentale a ensuite été menée pour tenter de quantifier l'impact de la présence de M. vison sur la faune autochtone. Cette étude a permis de souligner que les effets d'un prédateur introduit à court terme peuvent être moins évidents que présupposés. Enfin, nous nous sommes intéressés à la structuration génétique de la population et avons comparé la variabilité présente en Bretagne à celle d'autres populations férales européennes et des populations d'origine en Amérique du Nord. Une forte structuration génétique a été observée en Bretagne, et la présence de zones de contact et de mélange entre pools génétiques différenciés a été détectée. Ces résultats sont discutés dans une perspective de gestion à long terme des populations invasives de Vison d'Amérique

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Hammann, Mareike [Verfasser]. "Invasion ecology of marine macroalgae : the relevance of stress resistance for the invasion success of Gracilaria vermiculophylla and consequences of its spread / Mareike Hammann." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1153768542/34.

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Maybeck, Vanessa [Verfasser]. "Tools for non-invasive communication with electrogenic cells : optogenetic stimulation and diamond recording devices / Vanessa Maybeck." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1020471506/34.

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Basen, Timo [Verfasser]. "Nutritional aspects in the invasive freshwater bivalve Corbicula fluminea : The role of essential lipids / Timo Basen." Konstanz : Bibliothek der Universität Konstanz, 2012. http://d-nb.info/1026012732/34.

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Reid, Andrea. "Predicting peak refugia for mitigating impacts of invasive predatory fishes." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114304.

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Areas outside the distributional boundaries of an introduced predator may be exploited by native prey as refugia from predation. A classic example is the Lake Victoria basin of East Africa where hypoxic (low oxygen) wetlands serve as refugia for some native fishes from introduced Nile perch (Lates niloticus). In this thesis I quantified patterns of wetland refugia use in Lake Nabugabo, Uganda, a satellite of Lake Victoria, to achieve two primary goals: (i) identify peak refugia, where the greatest abundance and richness of native fishes persist, and (ii) directly link hypoxia tolerance of native and introduced fishes to their wetland distributions. A field survey indicated that peak refugia occur at the lake-wetland edge, and that strong edge-related gradients are shaping the fish assemblage structure of wetland habitats. Species richness and diversity were positively related to dissolved oxygen availability, and negatively related to temperature, pH, and vegetation density. Experiments quantifying the behavioural response of fish to progressive hypoxia revealed the highest tolerance to hypoxia in the swamp specialist Pseudocrenilabrus multicolor, when compared with three taxa found at the lake-wetland edge: juvenile endemic haplochromine cichlids, Nile tilapia (Oreochromis niloticus), and Nile perch. Tolerance to hypoxia decreased with increased body size in Nile perch, which may limit penetration of the wetland edge in larger-bodied Nile perch. By establishing a link between physico-chemical gradients and peak refugia our study points to the importance of invader-edge dynamics in determining the outcome of interactions between introduced predators and resident prey.
Les zones hors des frontières de répartition d'un prédateur introduit peuvent être exploitées par des proies indigènes comme refuge contre la prédation. Un exemple classique est le bassin du lac Victoria en Afrique de l'Est, où les zones humides hypoxiques (oxygène faible) servent de refuge pour certaines espèces de poissons indigènes de la perche du Nil (Lates niloticus) introduite. Dans cette thèse, j'ai quantifiée les modes d'utilisation des zones humides dans le lac Nabugabo, Ouganda, un satellite du lac Victoria, afin d'atteindre deux objectifs principaux: (i) identifier les refuges de pointe, où la plus grande abondance et richesse de poissons indigènes persistent, et (ii) relier directement la tolérance à l'hypoxie de poissons indigènes et introduits à leurs distributions dans les zones humides. Une enquête de terrain a indiqué que le refuge de pointe se trouve au bord du lac dans les zones humides, et que la structure des communautés de ces zones est liée aux gradients écologiques. La richesse et la diversité d'espèces étaient positivement liés à la disponibilité d'oxygène dissous, et négativement liés à la température, le pH, et la densité de végétation. Les expériences qui ont quantifier la réponse comportementale des poissons à l'hypoxie progressive ont révélés le plus haut taux de tolérance chez le spécialiste des marais, Pseudocrenilabrus multicolor, en comparaison à trois taxons présents au bord des zones humides: les cichlidés endémiques, la tilapia du Nil (Oreochromis niloticus), et la perche du Nil. La tolérance à l'hypoxie a diminuée selon la taille du corps chez la perche du Nil, ce qui peut limiter la pénétration des zones humides pour ce qui sont grandes. Cette étude démontre l'importance des dynamiques des refuges de pointe en déterminant les interactions entre les prédateurs introduits et les proies résidentes.

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Lee, Jongdae. "Studies on extracellular proteinases as virulence factors in invasive pulmonary aspergillosis /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487864485228814.

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Dissertations / Theses on the topic 'Invasie (biologie)'

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