The genetic basis and history of adaptive differentiation in high gene flow marine species – Hi-Flo

The originality of marine population genetics is to manipulate extreme values of demographic parameters, hardly ever observed in the terrestrial environment: high fecundity, huge population sizes and long distance dispersal via a planktonic larval stage. Correlatively, exceptionally high genetic diversity and low geographic differentiation are observed in many marine species. Local adaptation should be more costly for marine than for terrestrial species because larval movements exceed in scale the grain of habitat heterogeneity. Paradoxically, marine animals have proven able to pay the cost of local adaptation. We propose two hypotheses to resolve this old paradox of local adaptation in the sea: (i) A long history of non-equilibrium conditions (colonisation, range expansion, fragmentation) has a bearing on the existence and maintenance of environmental adaptation. (ii) Marine species are routinely structured into hidden differentiated endogenous backgrounds, so-called genetic barriers, which secondarily came to coincide with environmental transitions. The genetic basis and history of adaptive differentiation in marine conditions will be studied experimentally by population genomics approaches ('genome scan') and theoretically by incorporating pertinent variables in models and developing theoretical predictions tailored to the data gathered experimentally.