ИСТИНА

Partial COI genes for 23 individuals of Unio freshwater mussels, collected in Volga basin from 3 regions spaced by distances of 550 km in latitude and 1200 km in longitude were sequenced and analyzed using MrBayes and the MEGA7 programs. At phylogenetic trees, all sequences including obtained in this study fall into three major groups corresponding to three Unio species regardless methods of analysis. Note that sequences of geographically distant populations from West, Central and East Europe form homogenous species clusters.The levels of intra- and intergroup polymorphism for the COI gene estimated from genetic distances in Unio varied in range 0.001 – 0.004 and 0.036 – 0.152. Therefore, the values of intra– and interspecies genetic distances for the genus Unio did not overlap and are close to corresponding values obtained for other mollusks groups. Thus, the genus Unio is represented in the Volga basin by three species. Our data do not give grounds for the assumption of the existence of hidden species in the genus Unio.