Сhannelized Karyotype Evolution of the Common Shrew <i>Sorex araneus</i> (Mammalia)

Abstract

A model of channelized evolution of the S. araneus L. karyotype in the processes of replacement of ten pairs of acrocentric chromosomes by five pairs of metacentric chromosomes has been proposed. The channelized evolution of the karyotype arises due to the inability of Rb fusions with incomplete (monobrachial) homology to spread in the same population. Therefore, an Rb fusion, due to some random event first appearing in a population, largely determines the further evolution of the karyotype of that population. After the third replacement of acrocentric chromosomes by metacentric ones, the replacement of the remaining 6 pairs of acrocentrics allows the formation of no more than three karyotypes with five diagnostic metacentrics, which can be predicted, regardless of which rearrangements result in metacentric chromosomes (Rb fusion or WART). The channelized karyotypic evolution greatly increases the likelihood of parallel karyotype formation, in cases where evolution begins with identical metacentrics in geographically distant populations. An example of parallel evolution that began with the gk metacentric is the identical karyotypes of the new Mogilev race from Belarus and the Tomsk race from Western Siberia. The evolution of Eastern European chromosomal races shows hybrid fusion processes between the karyotypes of the East European karyotypic group (EEKG) and the West European karyotypic group (WEKG).