Sympatric area of Myodes glareolus and M. rutilus (Rodentia, Cricetidae): historic and recent hybridization

Abstract

The bank vole (Myodes glareolus) and the northern red-backed vole (M. rutilus) are two phylogenetically close sylvatic species with a widely sympatric range (European part of Russia, Western Siberia). A significant number of M. glareolus with mitochondrial genome of M. rutilus was detected in this sympatry zone earlier and only one of the first generation hybrid (F1) was discovered. The aim of the present study is to assess the extent of modern hybridization and to analyze the possible conditions of interspecies hybridization between the voles. The cytochrome b gene sequences of M. glareolus (164) and M. rutilus (108) sampled in the sympatric area were studied. In order to identify the modern hybrids, 841 individuals of M. glareolus were analyzed with cytochrome b PCR-typing, two microsatellite loci and one nuclear gene (LCAT). The detected unique case of the hybridization between M. glareolus and M. rutilus in nature is evidence that it is a possible at present but rare event. According to findings in the Urals M. glareolus populations, the chances of modern hybridization in the depression phases were higher than those regardless of cycle phase. Interspecific hybridization between these vole species in the historical past may have occurred in the southern Urals refuge during the Last Glacial Maximum, at a low density of both species. A mass independent hybridization during the formation of the sympatry seems less likely.