Soutenance de Thèse : Pierre Denelle

Soutiendra publiquement ses travaux de thèse intitulés
Nature et signature de l’optimalité dans l’assemblage des communautés

Soutenance prévue le mardi 4 juin 2019 à 13h30
Lieu : Amphithéâtre de la délégation régionale – CNRS

What drives taxonomical and functional turnovers of the assembly of organisms along environmental gradients? The idea that persistence and coexistence depend upon the adaptation to local environmental conditions constitutes a fundamental hypothesis. A phenotypic combination associated to a maximal per capita growth rate value then defines a local functional optimality. This notion of optimality motivates the study of trait ~ environment relationships in ecology and biogeography, and implies that a spe-cies with a phenotype close to the local optimum will be more abundant or have a more important biomass locally. Under this hypothesis, we expect that three funda-mental facets of performance, local abundances, per capita growth rates and ecologi-cal generalization, to be shaped by the distance to optimality along environmental gradients. However, other ecological processes such as competitive interactions be-tween species and dispersion from a regional pool of species can modify the ranking of local performance. How these processes affect the dimensions of performance of organisms is still misunderstood. This thesis then addresses the following questions: (i) how the functional composition within a regional pool of species and the local func-tional optimality jointly influence the functional composition of communities?, (ii) what is the functional signature of generalization along environmental gradients?, (iii) how additional processes can modify the trait ~ environment relationships?, (iv) how to infer the relative contributions of these processes from taxonomical and functional composition of communities? Mechanistic models and observed plant communities are used to answer these questions.

Keywords : Community assembly, Biodiversity scaling, Local functional optimality, Functional traits
Membres du jury:
M. Franck Jabot      LISC IRSTEA de Clermont-Ferrand    Rapporteur           
 M. Mathew Leibold  University of Florida           Rapporteur
 M. Nicolas Gross    UMR Ecosystème prairial INRA – Clermont-Ferrand   Examinateur
 M. David Mouillot    Um1 UMR - MARBEC Montpellier  Examinateur