Existence of two widespread semi-isolated genetic entities within Mediterranean anchovies

We investigated genetic transitions in European anchovies (Engraulidae) by analysing one mitochondrial and six nuclear microsatellite loci in samples from 28 geographical locations, primarily in the Western Mediterranean with external samples from the Black Sea in the East, and the Gulf of Biscay in the West. Four samples were collected from lagoons or shallow waters in France, Morocco and Tunisia. Two strongly differentiated loci and nucleo-cytoplasmic disequilibrium allowed us unambiguously to confirm the existence of a coastal genetic entity that is distinct from the more offshore marine populations. By contrast, four microsatellites were undifferentiated within the entire set of samples, testifying to a variable permeability of the two interacting genomes. Our findings strengthen and extend previous reports of the existence of a coastal anchovy entity that is widespread in Mediterranean lagoons.