Geographic variation of <i>Microtus middendorffii </i>(Cricetidae, Arvicolinae, Rodentia) sensu lato studied by craniometrical and mitochondrial features
Morphometric variation of voles <i>Microtus middendorffii </i>sensu lato and <i>M. gromovi </i>was examined based on 221 skulls. Molecular variation was assessed on partial sequences of cytochrome C oxidase subunit I gene (657 bp) from 23 individuals of <i>M. middendorffii </i>s.l. The observed pattern of variation within <i>M. middendorffii </i>s.l. corresponds to polytypic species comprising a number of geographic races. The taxonomic rank of the Ural and Yamal race (<i>M. m. ryphaeus</i>) is not lower than the rank of <i>M. m. middendorffii </i>and <i>M. m. hyperboreus</i>. Essential morphological differences within the scope of this study were found for the sample from the Kochechum River. The voles of <i>M. gromovi </i>are very similar morphologically to <i>M. middendorffii</i>. Taxa <i>M. middendorffii</i>, <i>M. gromovi</i>, and <i>M. mongolicus </i>form the single clade on the mitochondrial based tree, with <i>M. gromovi </i>as a basal taxon.