Biologie de l’invasion de Xenopus laevis en Europe : adaptations physiologiques et effets écologiques

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.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

De l'automatisation de l'affectation dans l'enseignement supérieur

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Differences in mobility at the range edge of an expanding invasive population of Xenopus laevis in the west of France

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Debootstrapping without Archeology

International audienceContext It is common for programming languages that their reference implementation is implemented in the language itself. This requires a "bootstrap binary": the executable form of a previous version of the implementation is provided along with the sources, to be able to run the implementation itself. Those bootstrap binaries are opaque; they could contain bugs, or even malicious changes that could reproduce themselves when running the source version of the language implementation-this is called the "trusting trust attack". A collective project called Bootstrappable was launched in to remove bootstrap binaries, providing alternative build paths that do not rely on opaque binaries. Inquiry Debootstrapping generally combines a mix of two approaches. The "archaeological" approach works by locating old versions of systems, or legacy alternative implementations, that do not need the bootstrap binaries, and by preserving or restoring the ability to run them. The "tailored" approach re-implements a new, non-bootstrapped implementation of the system to debootstrap. Currently, the "tailored" approach is dominant for low-level system components (C, coreutils), and the "archaeological" approach is dominant among the few higher-level languages that were debootstrapped. Approach We advocate for the benefits of "tailored" debootstrapping implementations of high-level languages. The new implementation needs not be production-ready: only to be able to run the reference implementation correctly. We argue that this is feasible , with several side benefits besides debootstrapping. Knowledge We propose a specific design of composing/stacking several implementations: a reference interpreter for the language of interest, implemented in a small subset of the language, and a compiler for this small subset (in another language). Developing a reference interpreter is valuable independently of debootstrapping: it may help clarify the language semantics, and can be reused for other purposes such as differential testing of the other implementations. Grounding We present Camlboot, our project to debootstrap the OCaml compiler, version. . Once we converged on this final design, the last version of Camlboot took about two human-months of implementation effort, demonstrating feasibility. Using diverse double-compilation, we were able to prove the absence of trusting trust attack in the existing bootstrap binaries of the standard OCaml implementation. Importance To our knowledge, this document is the first scholarly discussion of "tailored" debootstrapping for high-level programming languages. Debootstrapping recently grew an active community of free software contributors, but so far the interactions with the programming language research community have been minimal. We share our experience on Camlboot, trying to highlight aspects that are of interest to other language designers and implementors; we hope to foster stronger ties between the Bootstrappable project and relevant academic communities. In particular, the debootstrapping experience has been an interesting reflection on language design and implementation.

Resources allocated to reproduction decrease at the range edge of an expanding population of an invasive amphibian

International audiencePredicting the magnitude and nature of changes in a species’ range is becoming ever more important as an increas- ing number of species are faced with habitat changes or are introduced to areas outside of the species’ native range. An organism’s investment in life-history traits is expected to change during range shifts or range expansion because populations encounter new ecological conditions. While simulation studies predict that dispersal and reproductive allocation should increase at the range edge, we suggest that reproductive allocation might decrease at the range edge due to energy allocation trade-offs. We studied the reproductive investment of an invasive amphibian, Xenopus laevis, and measured reproductive allocation in three clusters of populations distributed from the centre to the edge of the colonized range of X. laevis in France. Resource allocation was estimated with the scaled mass index of gonads of both sexes during the local period of reproduction of the species. The level of resources allocated to reproduction was lower at the periphery of the colonized range compared to the centre and may be the result of changes in trade- offs between life-history traits. Such a pattern could be explained by interspecific competition or enhanced invest- ment in dispersal capacity

Multifactorial Analysis of Environmental Metabolomic Data in Ecotoxicology: Wild Marine Mussel Exposed to WWTP Effluent as a Case Study

International audienceEnvironmental metabolomics is a powerful approach to investigate the response of organisms to contaminant exposure at a molecular scale. However, metabolomic responses to realistic environmental conditions can be hindered by factors intrinsic to the environment and the organism. Hence, a well-designed experimental exposure associated with adequate statistical analysis could be helpful to better characterize and relate the observed variability to its different origins. In the current study, we applied a multifactorial experiment combined to Analysis of variance Multiblock Orthogonal Partial Least Squares (AMOPLS), to assess the metabolic response of wild marine mussels, Mytilus galloprovincialis, exposed to a wastewater treatment plant effluent, considering gender as an experimental factor. First, the total observed variability was decomposed to highlight the contribution of each effect related to the experimental factors. Both the exposure and the interaction gender × exposure had a statistically significant impact on the observed metabolic alteration. Then, these metabolic patterns were further characterized by analyzing the individual variable contributions to each effect. A main change in glycerophospholipid levels was highlighted in both males and females as a common response, possibly caused by oxidative stress, which could lead to reproductive disorders, whereas metabolic alterations in some polar lipids and kynurenine pathway were rather gender-specific. This may indicate a disturbance in the energy metabolism and immune system only in males. Finally, AMOPLS is a useful tool facilitating the interpretation of complex metabolomic data and is expected to have a broad application in the field of ecotoxicology

Rapid changes in dispersal on a small spatial scale at the range edge of an expanding population

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