Intra- and Interpopulation Odontological Variability in the Gray Red-backed Vole (Craseomys rufocanus) and Yu.I. Chernov’s Compensation Principle

— Methods of geometric morphometrics have been used to study geographic and chronographic forms of variation in the shape of the upper third molar (M3) in the gray red-backed vole C. rufocanus, a petrophilic rodent specialized to mountain habitats in the Urals. It has been shown that sexual dimorphism in M3 shape increases in the direction from the Southern to the Polar Urals. In the Middle Urals, differences in M3 shape (more distinct in males than in females) have been revealed between samples taken in years of high and low abundance of the species, which are apparently conditioned by a switch in tooth morphogenesis. This is suggestive of change in the morphofunctional properties of teeth and in related trophic preferences of males and females, i.e., in the possibility for them to consume different spectra of food resources. The increase in M3 sexual dimorphism in the south–north direction and in low-mountain biotopes (not common for the species) is in agreement with Chernov’s compensation principle manifested at the intra- and interpopulation levels, as it helps to alleviate trophic competition between males and females. The phenotypic plasticity of teeth provides for population-cenotic stability of the species in climatically unfavorable years and in atypical biotopes and environmental conditions of the Polar Ural Mountains.