Variability of Mitochondrial DNA Control Region and Phylogeography of Russet Ground Squirrel (Spermophilus major, Sciuridae, Rodentia)

Russet ground squirrel (Spermophilus major) is a widespread species with an extended range, partly separated by the Ural Ridge into eastern and western parts. Previously, a hybridization of the russet ground squirrel in contact areas with five other Spermophilus species, accompanied by a wide introgression of their mitochondrial genomes, was found. In the present work, a comparative analysis of the variability of the mtDNA control region of S. major was for the first time carried out throughout the range of the species (without taking into account introgressed haplotypes). It was demonstrated that species-specific haplotypes of S. major are distributed in all parts of its modern area and are characterized by a low level of intraspecific variability. The phylogeographic structure of the russet ground squirrel is slightly differentiated and does not form distinct geographically localized phyletic lines. In general, the range of the species is a single genetic space slightly separated by the Ural Mountains. The spatial distribution of haplotypes indicates the presence of an exchange between the western and eastern parts of the area in the Middle Urals. The indices of genetic diversity are evidence in favor of the expansive type of an increase in the population number, possible expansion of the range from the eastern part in the western direction, and short-term contacts of Cis-Ural and Trans-Ural northern populations. The results of the analysis of S. major genetic variability do not support the accepted subspecies system.