Phylogeography of the Common Vole Microtus arvalis, the Obscurus Form (Rodentia, Arvicolinae): New Data on the Mitochondrial DNA Variability

Genetic diversity of the common vole Microtus arvalis Pall., 1778 of the obscurus form was examined by analyzing the variability of two markers, the cytochrome b gene (1143 bp) and the fragment of the mitochondrial DNA control region (800 bp). One hundred forty-five individuals were captured at 39 locations from the Crimean Peninsula in the west to northern Altai in the east. On the basis of the analysis of the cytochrome b gene sequences, all M. arvalis individuals of the obscurus form from the regions under consideration were assigned to the previously identified Sino-Russian clade, distributed in the main part of the range of the obscurus form. On the basis of concatenated sequences of the two mtDNA markers, the internal structure of the Sino-Russian clade was established and two subclades, Crimean and Eurasian, were identified. In the Eurasian subclade, related haplotypes form several geographically localized groups (Vyatka–Ural, Volga–Ural, Southern Ural, Southern Cis-Urals 1, and Southern Cis-Urals 2). The groups are connected with each other through a widespread set of poorly differentiated haplotypes found from the Cis-Urals to Western Siberia. Two haplotypes from the North Altai and northern foothills of the Altai Mountains are included in the Eurasian subclade. However, these haplotypes are separated from each other and from haplotypes of other groups by distances comparable with the intergroup distance for this subclade. Demographic analysis enables the conclusion that the history of the Sino-Russian clade of M. arvalis of the form obscurus has regional specificity. Haplotypes found in seven locations on the Crimean Peninsula are most likely the result of a single expansion event, whereas for the Eurasian subclade, several successive waves of expansion can be proposed.