Morphotype analysis of the sibling vole (Microtus rossiaemeridionalis) casually introduced to the Russian Far East.

Here, we present the morphotypic variety of the m1 and M3 teeth diagnostics for the recently formed isolated population of the sibling vole in Far Eastern Russia. In the Far Eastern population, the prevalence of the individuals with m1 with a complicated crown of the forward unpaired loop of the paraconid is characteristic. Namely, m1 in these individuals shows well-expressed sixth exterior and fifth interior salient angles. The structure of the M3 morphotypes is also unique in the sibling voles in Far Eastern Russia. The dominant morphotypes were typica (47 %) and simplex (45 %), whereas the abundance of the duplicata morphotype was 0.08 %. The frequencies of various m1 and M3 morphotypes found in casually introduced sibling voles in the Far East are not typical of any previously studied Microtus rossiaemeridionalis population.