Hybrid zones between chromosome races of the common shrew in West Siberia

In West Siberia, the whole species range of the common shrew (Sorex araneus L.) is shared by two parapatric chromosome races — Novosibirsk and Tomsk. These races form a hybrid zone with each other. In addition, on the western margin of the range there is a hybrid zone between the Novosibirsk race and the Uralian race Serov, and in the east, the Tomsk race forms a hybrid zone with the East Siberian race Strelka hybrid. The structures of the three hybrid zones are very different and depend on the karyotypic state of the races in contact. A comparative analysis of the hybrid zones between the chromosome races of the common shrew in West Siberia is discussed together with the role of these zones in maintaining variability in natural populations.