Analysis of the Distribution of Robertsonian Fusions in Polymorphic Populations of the Common Shrew, Sorex araneus L.

We calculated the found and expected frequencies of metacentrics in polymorphic populations of the Dnieper basin common rodent, resulting from hybridization of local populations with acrocentric karyotype and four chromosomal races (Neroosa, Kiev, Białowieża, and Western Dvina) with 3–5 diagnostic metacentrics in each. We have previously shown an increased frequency of acrocentric karyotype compared to that expected according to Hardy-Weinberg. The low frequency (less than 0.5) of most metacentrics of the four chromosomal races and the disappearance of some of them from the populations can be explained by the increased fitness of the acrocentric karyotype and the absence of meiotic drive. On the contrary, the preservation of high frequency (more than 0.5) of such metacentrics as gm, hk (races of Western Dvina), hi (races of Kiev), hn, ik (races of Białowieża), and, especially, the fixation of metacentric hi (races of Neroosa) in polymorphic populations can be explained by meiotic drive. The fixation of Rb compounds in the range of the common rodent may be a consequence not only of gene drift, but also of meiotic drive. Most likely, meiotic drive is able to maintain the frequency of Rb compounds with the largest acrocentrics g, h, and i, which contributed to the widespread distribution of such compounds throughout the range of the common rodent.