KARYOTYPIC RACES OF THE COMMON SHREW (SOREX-ARANEUS) WITH EXCEPTIONALLY LARGE RANGES - THE NOVOSIBIRSK AND TOMSK RACES OF SIBERIA

Altogether 419 common shrews comprising 38 samples from 36 geographica lly-distinct sites in Siberia have been categorised as belonging to ei ther the Novosibirsk karyotypic race (XX/XY1Y2, af, bc, g/o, hn, ik, j /l, m/p, q/r, tu) or the neighbouring Tomsk karyotypic race (XX/XY1Y2, af, bc, g/k, hi, j/l, mn, o, p, q/r, tu). The most notable Robertsoni an polymorphism was that for arm combination qr present in both races that may reflect introgression after contact of the ancestral Novosibi rsk race (fixed for metacentric qr) and the ancestral Tomsk race (fixe d for acrocentrics q, r) at the end of the last glaciation. The Novosi birsk race occurs over a huge area (estimated at 700,000 km(2)) and is one of the most widespread karyotypic forms in S. araneus. Together w ith rather less extensive Tomsk race, these two races occupy much of t he range of the species to the east of the Ural Mts. We discuss how th e distributions of the Novosibirsk and Tomsk races were attained, in t he context of the Pleistocene-Holocene transition.