Genetic Variability of Three Isolated Populations of the Muya Valley Vole Alexandromys mujanensis Orlov et Kovalskaja, 1978 (Rodentia, Arvicolinae)

In the present study, on the basis of cytogenetic and molecular genetic (mtDNA control region) analysis, genetic variability of the Muya valley vole, Alexandromys mujanensis, an endemic of Buryatia and the northwest of Zabaykalsky krai, was assessed. Three isolated valley vole populations from the Muisko-Kuandinskaya and Barguzinskaya depressions, as well as the Baunt Lake valley, were examined. Polymorphism in the number of autosomal arms (NFa = 46–49) with a stable number of chromosomes (2n = 38), determined by morphological variability of four pairs of autosomes (MMUJ2, MMUJ7, MMUJ8, and MMUJ14), rather than two, as previously thought, was revealed. To date, for the Muya valley vole, ten karyotype variants have been identified. It seems likely that chromosomal rearrangements (pericentric inversions, as well as two variants of fusion of acrocentric chromosome pairs, i.e., centromeric-centromeric and centromeric-telomeric), which led to variability in autosome morphology in the populations of the Muya valley vole, are not harmful. Analysis of the mtDNA control region revealed high haplotype and nucleotide diversity for the species as a whole, while in the valley vole samples from the Dzherginsky Nature Reserve (Barguzinskaya Depression) and the Baunt lake valley, nucleotide diversity was reduced compared to the sample from the Muisko-Kuandinskaya Depression. Despite the fact that each of the studied populations has a unique composition of chromosomal rearrangements and mtDNA haplotypes, higher similarity between the populations of the Muisko-Kuandinskaya Depression and the populations of the Baunt lake valley can still be suggested.