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Evolution expérimentale et spécialisation dans le paysage adaptatif d'un gradient environnemental

Abstract : Today more than ever, it is crucial to anticipate and understand the evolutionary responses of living organisms faced with heterogeneous and unstable habitats. But to what extent is this possible? To reproduce an entire evolutionary trajectory, we must first describe the “material” available for adaptation (e.g. the phenotypic effects associated with the existing and novel genetic variability), and second describe the way evolutionary forces, shaped by the ecological context, result in specific “assemblies” of this material. At its simplest, this evolutionary process can be described by several cycles of mutation-selection events, leading to the adaptation of a population to an environment. This process is reflected in the evolutionary trajectories of bacterial lineages undergoing controlled experimental evolution in the lab. Concurrently, adaptive (phenotypic) landscape models, and especially Fisher’s geometrical model of adaptation, are powerful tools to formulate general predictions, which can then be tested on such evolutionary trajectories. However, they remain highly theoretical, and are widely conceived in a simple ecological context. In this thesis, we identified the (mutational and selective) determinants of the evolutionary trajectories of bacterial lines adapting to various environmental contexts. A first set of results regards evolution along a gradient of antibiotic doses, and their relevance is highlighted by experimental validation and by the reconstruction of the underlying adaptive landscape. A second experimental part integrates a biotic component (another bacteria) to the same environmental context. The evolutionary processes acting throughout the resulting long-term coevolution – maintained by frequency-dependent selection – are studied.
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https://tel.archives-ouvertes.fr/tel-01704551
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Submitted on : Thursday, February 8, 2018 - 3:17:06 PM
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  • HAL Id : tel-01704551, version 1

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Noémie Harmand. Evolution expérimentale et spécialisation dans le paysage adaptatif d'un gradient environnemental. Evolution [q-bio.PE]. Université Montpellier, 2017. Français. ⟨NNT : 2017MONTT062⟩. ⟨tel-01704551⟩

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