Genetic Differentiation within Two Large Phylogroups of the Common Hamster (Cricetus cricetus) (Cricetidae, Rodentia), Boundary, and Population Size

In 2022 the present authors described the mitochondrial lineage “Altai” (“A”), the most recent of the three phylogroups of the common hamster, occurring in Russia and Kazakhstan. However, the limits of its current distribution and population size required clarification. In the course of our special expedition, tissue samples of the common hamster were collected in 12 regions of Russia and Kazakhstan, including areas at the potential boundary between the ranges of phylogroups A and E (“Europe”). Analysis of the nucleotide sequences of the cytochrome b (cytb) gene of the trapped animals has shown that the boundary between these phylogroups runs between Turinsk and Yekaterinburg, next between Chelyabinsk and Kurgan, and between Omsk and Tatarsk, and diverts southward, heading away from the village of Turgai and the city of Temirtau in the west and the village of Bayanaul in the east. The structure of territorial genetic clades, belonging to phylogroups A and E, and the history of their formation were also analyzed. Most of the territorial clades detected formed during the Late Pleistocene and Holocene. The analysis of population dynamics in phylogroups A and E showed its decline in eight of the 12 regions surveyed.