Comparative studies of ecological niche variation among central and peripheral populations of Mediterranean endemic plants

The Mediterranean basin is a biodiversity hotspot, characterized by its high plant richness and endemism. It is a place of prime interest to test biogeographical hypotheses, such as the centre-periphery hypothesis. Empirical evidences have brought little support to it as a rule, suggesting complex eco-evolutionary mechanisms shape genetic and demographic characteristics.This thesis proposes a new framework that supports a precise evaluation of species history, geography and ecology to investigate genetic and demographic variation. In this perspective, we set up a study of 11 Mediterranean vascular plants to investigate changes in the micro-ecological niche between central and peripheral populations. Several shifts appeared which emphasized the ecological originality of peripheral population. Peripheral populations subsist in cooler and wetter climate compared to their mean central relatives, but are not marginal regarding their climatic niche. Several species presented similar distribution patterns on restricted areas in France, which may result from their persistence in micro-refugia during Pleistocene glaciations. This historical perspective was fundamental to explain patterns of floral polymorphism in Narcissus dubius. Spatial isolation and ecological originality confer to peripheral isolates a high evolutionary potential, and understanding fine scale ecological characteristics and distribution history is essential to shed light on processes driving plant diversity.