Genetic Variation and Differentiation of Wood Mice from the Genus Sylvaemus Inferred from Sequencing of the Cytochrome Oxidase Subunit 1 Gene Fragment

To ascertain intra- and interspecific differentiation patterns of some Sylvaemus wood mice species (S. uralensis, S. sylvaticus, S. ponticus, S. flavicollis, and S. fulvipectus), sequence variation of the fragment (654 bp) of the mitochondrial cytochrome oxidase subunit I gene (COI) was analyzed and the data obtained using several molecular genetic markers were compared. Distinct isolation of all Sylvaemus species (including closely related allopatric S. flavicollis and S. ponticus), as well as of the European and Asian races of pygmy wood mouse S. uralensis at the COI gene was demonstrated. However, genetic differences of the Sylvaemus species were 1.5 times and more higher than the distance (D) between the races of S. uralensis. This finding provides no ample grounds to treat them as the independent species. The only examined specimen of Pamir-Alay subspecies S. uralensis pallipes showed closest relatedness to to the Asian race, although was rather distant from it (D = 0.038). No reliable isolation of the eastern European and southern European chromosomal forms, representing the European race of S. uralensis, as well as of their presumptive hybrids from the outskirts of the city of Sal'sk, Rostov region, at the COI gene was revealed. A hybrid origin of the population of pygmy wood mouse from the outskirts of the Talapker railway station, Novovarshavsky district, Omsk region, was confirmed (in preliminary studies, based on karyotypic characters, these specimens were diagnosed as distant hybrids of the eastern European chromosomal form and the Asian race). In yellow-necked wood mouse S. flavicollis from the territory of Russia and Ukraine, weak differentiation into northern and southern lineages (with mean genetic distance between them of 0.020) was observed. Considerably different relative genetic distances between the races of S. uralensis and the S. flavicollis-S. ponticus species pair, inferred from the mitochondrial cytochrome oxidase and cytochrome b genes data, indicated that the rates of evolution of the mitochondrial genome regions could be very dissimilar. It is suggested that transformations of the cytochrome b gene, or at least its part, were irregular in time and/or in different phyletic lineages (i.e., accelerated upon the formation of pygmy wood mouse races, and delayed upon the establishment of S. flavicollis and S. ponticus). DOI: 10.1134/S1022795412020044