Mitochondrial variability of sand smelt Atherina boyeri populations from north Mediterranean coastal lagoons

The role of transition environments, such as lagoons or deltas, in shaping the geographical pattern of genetic variability may be investigated through the analysis of population structure in the species living in these habitats. Several fish species are strictly bound to deltas or coastal lagoons for at least part of their life cycle. This paper reports the analysis of mitochondrial DNA variability in several populations of Atherina boyeri (Risso, 1810) sampled along the north Mediterranean coasts from the Atlantic Ocean to the Black Sea. The results show a high genetic structure among populations, probably due to the deep fragmentation of the lagoon environments in which this species spends most of its life cycle. On the other hand, a clear phylogeographic pattern and a significant positive correlation between genetic and geographical distances support the hypothesis of gene flow among populations, probably due to an imprecise anadromic behaviour from the lagoons to the close coastal sea, which allows for an exchange of individuals between contiguous populations. Our results are in good agreement with those previously obtained on the same species by RAPD techniques. Our analysis among different Atherina genera are also compatible with the most recent classification of these species based on morphological and genetic characters.