Do discrepancies between microsatellite and allozyme variation reveal differential selection between sea and lagoon in the sea bass (Dicentrarchus labrax)?

In the present study the genetic structure of Dicentrarchus labrax (14 samp les from the Mediterranean) was analysed at six microsatellite loci, in ord er to test the hypothesis that some enzymatic loci undergo selection betwee n marine and lagoon habitat. Eight of the 14 samples were analysed at both microsatellite and allozyme markers. The analysis of the genetic variation among the Mediterranean samples showed that (i) (F) over cap(ST) values obt ained with the six microsatellite loci were much smaller than those obtaine d with the 28 allozymes and (ii) microsatellite loci seemed to reflect more the geographical proximity than an ecological one. Thirteen enzymatic loci exhibited moderate to high values compared with microsatellites. This was interpreted as evidence that these allozymes are non-neutral. However, only six loci seemed to be implicated in differentiation between marine and lag oon samples, the causes of selection being unknown for the others. A possib le scenario of population dynamics of the sea bass between marine and lagoo n habitat is suggested.