New data on chromosomal variability, distribution of sibling species, and hybridization of 46-chromosomal forms of Microtus arvalis sensu lato (Rodentia, Arvicolinae) in the Upper Volga basin

Abstract

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.