We studied molecular variability to clarify intraspecific differentiation and phylogenetic relationships in three pine vole species (genus Microtus, subgenus Terricola): Microtus subterraneus, Microtus daghestanicus, and Microtus majori. Multilocus analysis was performed using the entire mitochondrial cytb gene and fragments of nuclear BRCA1, IRBP, and XIST genes. Results confirmed separation of the species, especially M. majori compared with M. daghestanicus and M. subterraneus. These species showed different molecular polymorphism in the genetic markers. We identified two close forms of M. majori, differing in cytb gene and the nuclear gene XIST; one form inhabits the northern slopes of the Greater Caucasus, another the Transcaucasia. Separation of M. daghestanicus populations from North Ossetia and the others was clear. Microtus subterraneus populations from southern Europe and Asia Minor were characterized by maximal genetic heterogeneity; the specimen from Samsun (northern Asia Minor) appeared to be most distant from the others. Despite polymorphism in the chromosome number in M. subterraneus populations from the East European Plain, they possess a depleted gene pool. Results indicated that M. subterraneus colonized the East European Plain in the Holocene, and chromosome variability originated in this part of the species' range as a result of chromosomal fission and quick fixation of the arrangement in northern populations. We argue that differences in the genetic differentiation patterns of Terricola species are mainly due to their ecological peculiarities.

New data are presented on the composition, intraspecific structure, and geographic distribution of the sibling species of common voles in the Upper Volga basin and on the occurrence frequency and temporal dynamics of the complex chromosomal rearrangement of autosome pair 5 in Microtus arvalis f. obscurus in populations from Nizhny Novgorod region. A total of 100 M. arvalis s. l. from 18 localities of the region have been identified by methods of chromosomal analysis (routine and AgNOR staining, C- and G-banding). The forms of M. arvalis s. l. distinguished in the sample include M. rossiaemeridionalis (n = 4), M. arvalis f. obscurus (n = 82), M. arvalis form arvalis (n = 11), and F₁ hybrids between the last two forms (n = 3). These results confirm the concept of M. arvalis s. l. taxonomic diversity in the Upper Volga basin and contribute to the cadasters of M. rossiaemeridionalis, M. arvalis f. arvalis and M. arvalis f. obscurus. In addition, they allow a more accurate delimitation of the distribution boundaries of 46-chromosomal M. arvalis s. l. forms in the Upper Volga basin and are indicative of hybridization between them in Nizhny Novgorod region (Sokolsky district), where M. arvalis f. arvalis and F₁ hybrids have been recorded for the first time.

A review of original and published data on invasions of sibling species of Microtus from the group “arvalis” (East European vole, M. rossiaemeridionalis; common vole, M. arvalis; and Altai vole, M. obscurus) is given. Two stages of invasions differing in duration are established. These stages defined the formation of the modern ranges of these species and had an influence on evolutionary processes. The first stage is connected with agricultural development of Eurasia from the early Neolithic to the broad plowing of lands in the second half of the 20th century. Northern expansion of the range following the deforestation for plowing uses and southern expansion as a result of irrigation of arable lands are peculiar to all three sibling species. The second stage is due to expansion of the transport network and growth of traffic in the 20th century. The latter is characteristic of M. rossiaemeridionalis. The natural and historical reasons for the formation a contact zone between M. arvalis and M. obscurus are reconstructed. Original maps of the modern distribution of sibling Microtus species of the “arvalis” group, as well as natural and historical factors that influenced the formation of their ranges, are provided.

To specificate phylogenetic relationships between sibling-species Sicista of the caucasica group and to determine their position in the genus Sicista, comparative analysis of the nucleotide sequences...

Results of the analysis of IRBP (interphotoreceptor retinoid-binding protein) nuclear DNA gene variability in birch mice of the genus Sicista reflect monophyly of the betulina group and confirm the substantial genetic isolation of the sibling species S. betulina and S. strandi within this group. Using Tamura’s 3‑parameter model T92, it is shown that the mean genetic distances between S. betulina and S. strandi are 0.7%, comparable to the interspecific genetic distances for sibling species from other groups of birch mice. Their intraspecific differentiation, which is particularly well-expressed in S. strandi, is also identified. Differentiation between the northern and southern populations of S. strandi, comparable to the interspecific differences (D = 0.8%), and isolation of the Carpathian specimen of S. betulina from other European and Siberian sample sets (D = 0.2%) are shown.