Distribution and genetic diversity of two species of
Pelasgus (Leuciscidae) is a freshwater fish genus endemic to the Southern Balkans. The distribution of most of its species is insufficiently known. Pelasgus was molecularly studied only marginally, and the genetic diversity of individual species or populations, crucial for their conservation, is completely unknown. We studied distribution and genetic diversity of Pelasgus stymphalicus (Valenciennes 1844) and Pelasgus marathonicus (Vinciguerra 1921), two widespread species from southern Greece. Our data, based on cytochrome b sequences, confirmed that a number of populations whose taxonomic status had been uncertain, belong to one of these species. The distribution range of P. stymphalicus includes the Ionian mainland, from the Acheloos to Mornos rivers, and most of the Peloponnese, excluding the Evrotas and the headwaters of Alfios. The native range of Pelasgus marathonicus is the western Aegean mainland, from rivers near Athens to the Xerias river in the Pagasitikos Gulf. AMOVA showed that the genetic variance is slightly higher among than between populations. High FST values indicated a pronounced genetic differentiation of the populations in both species. There was a high proportion of private haplotypes and a very small number of shared haplotypes between populations in both species, which indicates uniqueness of each population and their susceptibility to human-induced changes.