Unusual chromosomal polymorphism of the common shrew, L., in southern Belarus.

Analysis of the frequency of karyotypes and chromosomal rearrangements in the distributional ranges of four metacentric races of Linnaeus, 1758 has revealed features that are not typical for polymorphic populations of this species. The frequency of the acrocentric karyotype and heterozygotes for fusion of acrocentric chromosomes turned out to be significantly higher than expected in case of random crossing. As an explanation for the unusual polymorphism, it has been suggested that metacentric races may hybridize with acrocentric populations that remained from the ancient chromosomal form.

Karyotypic differentiation of populations of the common shrew L. (Mammalia) in Belarus.

The common shrews, Linnaeus, 1758, inhabiting the territory of Belarus, are characterized by a significant variation in the frequency of Robertsonian (Rb) translocations. The frequency clines for translocations specific of three chromosome races: the West Dvina (, , , ), Kiev (, , , , , , ), and Białowieża (, , , , , ) have already been studied in this territory. In this communication we report new data on polymorphic populations with Rb metacentrics specific of the Neroosa race (, , , , ) in south-eastern Belarus, analyse the distribution of karyotypes in southern and central Belarus and draw particular attention to the fixation of the acrocentric variants of chromosomes in this area.