Aire de répartition

Résumé

vignette|Exemples d'aires de répartition d'espèces vivantes. L’aire de répartition, appelée aussi aire de distribution ou simplement distribution, est la zone délimitant la répartition géographique d'une espèce vivante ou de toute autre unité taxonomique qui inclut la totalité de ses populations. L'aire d'une espèce peut être continue ou au contraire disjointe (répartition en métapopulations). L'étude descriptive de la répartition géographique des espèces vivantes est la géonémie et celle explicative de ses causes est la chorologie. Différence entre « aire de répartition » et « répartition spatiale d'une population » L'aire de répartition géographique ne doit pas être confondue avec la répartition spatiale d'une population qui est la modalité de répartition à l'intérieur d'un biotope des individus constituant une population d'une espèce déterminée. Notion relative Les aires de répartition grandissent et se réduisent au fur et à mesure de l'évolution et de la d

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Publications associées (63)

Current and future spatial distribution of ticks (Ixodes ricinus) and of hosted Chlamydia in Switzerland

Morgan Bruhin

This project aims to study the spatial distribution of tick, I. ricinus, and emergent Chlamydiales families hosted by them. We used presence data associated with environmental variables to construct habitat suitability indexes by using species distribution modeling from the Maxent software. Most of the variables are climatic coming from the Worldclim website, also available for future climatic predictions. Additionally, the possible evolution of those habitats was estimated considering future climate conditions in 2070. We applied the previous species distribution modeling method with predictive variables to characterize their evolution. Finally, an estimation of the population exposed to this possible emergent threat to the human health under the form of a synthetic index. This index regroups the relative population density with the combination of the possible habitat of the tick and the hosted Chlamydiae. The results showed an expected general presence over the low altitude areas for the tick, but the predictive model failed to clearly identify areas of possible important modification of their suitable habitat. The Chlamydiae also admitted a possible habitat over most of the low altitude, mostly the Plateau. Their future evolution seemed to point out a homogenization of the distribution for those families over the Plateau.

2016

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Climate change threatens biodiversity and species distribution all over the world at unprecedented rates. Human induced changes to landscape structure and habitat are redefining the relation between species and their environment. Understanding, characterizing and modeling the relation between complex landscape features and geographical species presence, the subject of this thesis, have thus gained paramount importance in order to make informed decisions on near- and far-term management strategies for species and landscape protection. The present thesis pays particular attention to the understanding of how mountain landscapes, described as heterogeneous habitat matrices, govern the presence of a species in space and time. To this end, throughout this thesis a metapopulation model is considered, a spatially-explicit model based on the balance between colonization and extinction events in areas of different suitability. The classical patch-based modelling approach is extended here in various ways in order to incorporate landscape-explicit information about the habitat matrix. A first theoretical study is performed on geometric, realistic, and real landscapes which highlights how different levels of connectivity, the degree to which different areas of similar habitat are actually linked together in the landscape (say, derived from geomorphic structures, such as valleys and peaks or emerging structures shaped by fluvial erosion and tectonic uplift) impact the dynamic of mountain species under climate change. A second, applied, study investigates how different landscape descriptors derived from Earth Observation data can be used in order to dynamically model the spatial, landscape-explicit, presence of two carabid species (Pterostichus flavofemoratus and Carabus depressus) in the Gran Paradiso National Park. In a final study, the consistency of the metapopulation model is investigated when considering different resolutions of the landscape matrix, i.e. different levels of coarse-graining. This last part is fundamental to the understanding of how conclusions drawn from local studies can be made general and extrapolated to larger regions. Overall, this thesis bridges the fields of population and landscape ecology, focusing on modelling metapopulation dynamics in complex landscapes seen as the substrate for ecological interactions. The result from the three studies show that metapopulation ecology can profit from the insights of landscape ecology. The combination of the two fields can be a useful tool in furthering the understanding and monitoring of mountain species.

EPFL2020

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Bacteria-induced mixing in natural waters

Oscar Rodrigo Sepúlveda Steiner, Talia Ekin Tokyay Sinha, Alfred Johny Wüest

Swimming organisms can enhance mixing in their natural environments by creating eddies in their wake and by dragging water along. However, these mixing mechanisms are inefficient for microorganisms, because swimming-induced variations in velocity, temperature, and dissolved substances are evened out before they can be advected. In bioconvection, however, microorganisms induce water movement not by propulsion directly but by locally changing the fluid density, which drives convection. Observations of bioconvection have so far mainly been limited to laboratory settings. We report the first observation and quantification of bioconvection within a stratified natural water body. Using in situ measurements, laboratory experiments, and numerical simulations, we demonstrate that the bacterium Chromatium okenii is capable of mixing 0.3 to 1.2 m thick water layers at around 12 m water depth in the Alpine Lake Cadagno (Switzerland). As many species are capable of driving bioconvection, this phenomenon potentially plays a role in species distributions and influences large-scale phenomena like algal blooms.

2017

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EPFL2020