B chromosome in Plantago lagopus Linnaeus, 1753 shows preferential transmission and accumulation through unusual processes

The common shrews, Sorex araneus 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 ( gm , hk , ip , no, qr ), Kiev ( g/m , hi , k/o , n , p , q , r ), and Białowieża ( g/r , hn , ik , m/p , o , q ) 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 ( go , hi , kr , mn , p/q ) 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. The results show that certain Rb metacentrics specific of the Neroosa, West Dvina, Kiev, and Białowieża races (namely, go and pq ; ip ; ko ; hn and ik , respectively) are absent in many polymorphic populations. Thus, the karyotypic differentiation of S. araneus in the studied area is determined by unequal spread of different Rb translocations and by fixation of acrocentric variants of specific chromosomes.