Comparative pattern of genetic structure in two Mediterranean killifishes (Aphanius fasciatus and A. iberus) inferred from both mitochondrial and nuclear data

In this study, genetic variation was assessed in Aphanius fasciatus and Aphanius iberus characterizedby similar ecological traits but with very different distribution ranges in the Mediterranean area. Fivepopulations of A. iberus and five of A. fasciatus were analysed using five polymorphic microsatelliteloci and partial mitochondrial control region (D-loop) sequences. Congruent results were found withboth nuclear and mitochondrial molecular markers. The results showed that similar levels of geneticdivergence, based on mitochondrial control region sequences, are present among populations of A.iberus and among populations of A. fasciatus despite the very different geographic distance existingamong the examined populations of the two species (low geographic distance in A. iberus and highin A. fasciatus). A possible explanation could be that the populations of A. iberus were isolated for alonger time than the populations of A. fasciatus supporting the hypothesis that the split in the lineageleading to A. iberus is older than the split in the lineage leading to A. fasciatus. The possibility that thewide circum-Mediterranean distribution of A. fasciatus ensures the high connectivity of its populations,preventing, in some cases, local differentiation, however, cannot be ruled out.