The utility of DNA Barcoding for species identification and discovery has catalyzed a concerted effort to build the global reference library; however, many animal groups of economical or conservational importance remain poorly represented. This study aims to contribute DNA barcode records for all ground squirrel species (Xerinae, Sciuridae, Rodentia) inhabiting Eurasia and to test efficiency of this approach for species discrimination. Cytochrome c oxidase subunit 1 (COI) gene sequences were obtained for 97 individuals representing 16 ground squirrel species of which 12 were correctly identified. Taxonomic allocation of some specimens within four species was complicated by geographically restricted mtDNA introgression. Exclusion of individuals with introgressed mtDNA allowed reaching a 91.6% identification success rate. Significant COI divergence (3.5–4.4%) was observed within the most widespread ground squirrel species (Spermophilus erythrogenys, S. pygmaeus, S. suslicus, Urocitellus undulatus), suggesting the presence of cryptic species. A single putative NUMT (nuclear mitochondrial pseudogene) sequence was recovered during molecular analysis; mitochondrial COI from this sample was amplified following re-extraction of DNA. Our data show high discrimination ability of 100 bp COI fragments for Eurasian ground squirrels (84.3%) with no incorrect assessments, underscoring the potential utility of the existing reference librariy for the development of diagnostic ‘mini-barcodes’.

In four ground squirrel species from the Volga region—yellow ( Spermophilus fulvus), russet ( S. major), little ( S. pygmaeus), and speckled ( S. suslicus)—four hybridization variants (major/fulvus,...

DNA studies of badgers (Meles sp.) from the right-bank and left-bank areas of the Volga river in the Saratov region are described. Asian badgers (Meles leucurus Hodgson, 1847) inhabit the Left Volga Bank of the Saratov region, while European badgers (M. meles Linnaeus, 1758) inhabit the Right Volga Bank districts of the region, but Asian badgers were found in Khvalynsky district of the Saratov region, besides the European badger. Despite a sufficient number of publications devoted to the Asiatic badger distribution in the Vyatka–Kama region and the Volga region, and studies devoted to the development of systematics of the genus Meles in Russia, the question of the boundaries of the ranges of European and Asiatic badgers and the zones of their sympatry (parapatry) in the Volga–Kama region has not been fully investigated to date. Our work is devoted to the study of this question. As a result of analyzing the biological material collected by us, it was found that all five studied individuals of badgers from the Saratov Volga region phenotypically looked like Asian badgers, but our DNA analysis showed that only two of them were M. leucurus, whilst three ones were heterozygous individuals carrying genes from both species and were identified as hybrids. The remaining 29 individuals were captured in the right-bank areas of the region. Badgers were sampled from individuals from the northern to southern borders of the region in areas located along the Volga river on the Volga upland and in the Oka–Don plain. Of these, one individual from Khvalynsky district turned out to be an Asian badger, one individual from Krasnoarmeysky district was a hybrid of the two named species, and three individuals, one from Tatishchevsky, the second from Volsky and the third from Khvalynsky districts showed introgression of Asian badger genes into the genotype of the European badger. Thus, we have managed to find out that at this stage of development of the phase of the climatic cycle in the Lower Volga region, characterized by warming winters, the Volga river, with its two reservoirs within the Saratov region, is not an absolute zoogeographical boundary, and badgers, whose species are characterized by winter sleep, can in certain conditions overcome, most likely on ice, both the river itself and the lake parts of the Volgograd and Saratov reservoirs. According to the revealed introgression in some individuals from different areas on the Volga upland of the right bank of the Saratov region, it can be assumed that such traveling across the Volga river took place earlier, possibly before its flow was regulated by dams.

The research into the structure, population and genetic patterns of the formation and long-term existence of natural hybrid zones, and the role thereof in microevolution and speciation is critical for modern biology and the evolution theory. The article presents the research results on the 25 year-monitoring (1996–2022) of the sympatric zone and contact colonies of russet (Spermophilus major Pallas, 1778) and speckled (Spermophilus suslicus Güldenstaedt, 1770) ground squirrels. This zone of sympatry arose as a result of S. major invasion due to its resettlement from the left-banked Volga regions in the second half of the 1900s. One hundred and eighty-two rodent colonies, peculiar for different periods of researches, were studied. In total, 870 individuals were trapped and sampled (including 567 individuals of S. major, 253 individuals of S. suslicus, and 50 genetically confirmed interspecific hybrids). Based on actual data, the article discusses the structure and factors for the formation of russet and speckled ground squirrel sympatric zone; the metapopulation structure of species-area relationships; the features of joint, mixed and hybrid colonies; the evolution of hybrid population. The hybridization between russet and speckled ground squirrels has evidenced a sporadic introgressive and interspecific hybridization over a broad zone of sympatry with a random occurrence of hybrid colonies. The revealed structural features of the hybrid zone of S. major and S. suslicus have enabled it to be termed as a bimodal hybrid zone of an ecological type.