A wide hybrid zone of chromosome races of the common shrew, Sorex araneus Linnaeus, 1758 (Mammalia), between the Dnieper and Berezina Rivers (Belarus)

Karyological study of 75 specimens of the common shrew, Sorex araneus Linnaeus, 1758, from 8 localities in the Berezina River basin (eastern Belarus) was carried out. A wide hybrid zone (not less than 100 km) between the northern West Dvina chromosome race (XX / XYY, af, bc, gm, hk, ip, jl, no, qr, tu) and the southern Turov race (XX / XYY, af, bc, g, h/k, i, jl, m, n, o, p, q, r, tu) was revealed in this region. Frequencies of fused-unfused arms comprising four diagnostic metacentrics of the West Dvina race (g/m, h/k, n/o, q/r) were calculated in all capture sites. Taking into consideration the absence of metacentric ip in specimens from six northern localities, the Borisov (Bs) race (XX / XYY, af, bc, g/m, h/k, i, jl, n/o, p, q/r, tu) (Orlov, Borisov, 2009) was distinguished in these sites. Common shrews from two southern localities on the right and left banks of the Berezina River (Berezino vicinity) were referred to the Turov race. The presence of four metacentrics descended from the West Dvina race in the Bs race testifies to the hypothesis expressed earlier that the polymorphic populations of the S. araneus between the Dnieper and Berezina Rivers originated as a result of the West Dvina race spreading from the north and of hybridization between this race and local populations with acrocentric chromosomes.