Phylogeography and population structure of Ponticola gorlap (Teleostei: Gobiidae) in an evolutionary distinctive and ecologically threatened Caspian Sea sub-basin

The South Caspian Sea sub-basin, owing to its complex paleogeographic history and habitat diversity, represents a center of endemism and a high-priority conservation area for the gobiid genus Ponticola . However, very little is currently known about most biological aspects of these species in general, and this sub-basin is highly threatened by anthropogenic activities. Here we examined the phylogeographic patterns, genetic diversity, and population structure of the endemic Caspian Sea species P. gorlap , in this evolutionary distinctive and ecologically threatened Caspian sub-basin. Mitochondrial DNA control region sequences and otolith shape variations were analyzed from 472 individuals at seven South Caspian localities. Results showed: (i) two shared and eight private haplotypes, distinguished by shallow divergences, (ii) pairwise Φ ST values among locations, ranging from − 0.052 to 1.00; with most of the highest between Sefidroud/Kaboudval and the other samples, (iii) genetic diversity was generally low, smaller at Kaboudval/Nekaroud, and highest at Babolroud, (iv) non-unimodal mismatch distribution and neutrality tests both rejected a recent demographic expansion scenario, (v) otolith shape analysis revealed significant differences among samples, the highest between Sefidroud/Kaboudval and the others, and (vi) Mantel tests confirmed that both pairwise Φ ST and otolith shape differences were more correlated to each other than with geographic distances. Different scenarios are discussed to explain the observed patterns of genetic and otolith shape variations and population structure of P. gorlap , including possible roles of euryhalinity, and presence of migratory and resident forms.