| Summary: | The context related to global change and risks of biodiversity loss have led managers to develop tools to help preserve our environment and the associated biodiversity. Many questions have been raised especially concerning the connectivity between populations and the definition of marine protected areas. These questions raise the problem of dispersal abilities and of the relationship between pelagic larval duration and gene flow. In this context we have chosen to study the connectivity between populations of two species of high commercial and patrimonial values: the edible sea urchin Paracentrotus lividus and the white seabream Diplodus sargus. In the case of P. lividus, the study combining several data sets and using different molecular markers, produced during this work or obtained from the literature, showed unexpected significant genetic differentiation at the regional scale (40km) for a species with a pelagic larval duration of up to one month. This study also allowed us to characterize the intensity and direction of gene flow between ocean basins of the southeastern North Atlantic, Mediterranean Sea and Adriatic Sea. Indeed gene flow was asymmetric and oriented from the Atlantic to the Mediterranean Sea and from the Adriatic Sea and to the Mediterranean Sea. These findings raise important questions about the origin of these different levels of differentiation and led me to make several assumptions on the impact of phenomena such as local adaptation, selective effects coupled with endogenous barriers, hydrological factors and / or biogeochemical. Several research perspectives are proposed to test these hypotheses. Le contexte lié au changement global et aux risques encourus par la biodiversité ont conduit les gestionnaires à développer des outils afin de préserver notre environnement et la biodiversité De nombreuses questions ont alors été soulevées notamment au sujet de la connectivité entre populations à préserver et de la définition des aires protégées. En milieu marin cette question soulève le ...
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