Phylogenetic and population genetic analysis of Thymallus thymallus (Actinopterygii, Salmonidae) from the middle Volga and upper Ural drainages

Abstract

The evolutionary relationship of grayling populations from the Kama and upper Ural drainage was studied, and the genetic diversity of the local populations was assessed. The complete mitochondrial DNA control region was sequenced and 12 microsatellite loci genotyped. Five previously undescribed closely related haplotypes (Caspian clade) were detected. The Caspian and previously reported Scandinavian clade formed a Caspio–Scandinavian group that was found to be the closest relative to the Balkan clade of European grayling. Based upon the molecular results, paleogeological information and a molecular clock of 0.5% change per million years, it appears the Caspio–Scandinavian group split some 0.6 million years ago (95% HPD = 0.33–0.92 mya), while the Balkan clade separated about 1 mya, in the Pleistocene. The sister relationship between Caspian and Scandinavian haplotypes implies that, at some time over that period, the Caspian basin might have been a corridor for dispersal connecting eastern and northern Europe. Microsatellite analysis revealed relatively large inter-population genetic differentiation among the Caspian sample set, pointing to genetically distinct populations that are deserving of special attention in terms of management and conservation.