Comparative phenetical analysis of populations of two rodent species (Apodemus, Mus) in the Central Caucasus

Variation of 20 nonmetrical cranium characters in 197 specimens of the lesser common field mouse and in 204 specimens of the house mouse from 4 geographical sites of the Central Caucasus have been studied considering two factors: anthropogenic pollution and altitude of locality. A species-specific reaction to the effect of anthropogenic pollution and the altitude of locality factor was revealed. This is reflected in a dissimilar pattern of changes in the frequency of phenes in the studied rodent species. Based on phenetic distances, it is found that the anthropogenic and control, as well as middle highland and foothill samples of a field mouse are distinguished largely than those of a house mouse. It is suggested that the lesser differentiation level in the samples of the house mouse is caused by more favourable living conditions, and therefore by lesser susceptibility to the environmental factors. The second possible reason may be as follows: the populations of the house mouse are more susceptible to genetic exchange through periodic invasion from other regions, which probably leads to a leveling of epigenetic differences.