In Western Siberia, most boundaries between common shrew chromosomal races have been found to pass along the banks of rivers, mainly those flowing in the meridional direction. The races Serov and Novosibirsk co-inhabited the right bank of the Irtysh. The easternmost point of the Novosibirsk race has been found on the middle Yenisei River, while the race Tomsk in this area was only on the right (eastern) bank.

We studied the polymorphism of the cytb gene in two forms of the Lesser White-toothed Shrew species complex: Crocidura suaveolens s. stricto and C. sibirica. The haplotypes of C. sibirica are found to be very similar to those of Crocidura suaveolens. They do not belong to a distinct haplogroup. The molecular diversity of the populations in the Asian part of the range is higher than in Eastern Europe. For the combined sample from Asia and Europe together, we revealed a significant signal of population expansion. Analysis of the expansion time showed that the Asian territory was colonized earlier (before the last glacial maximum) than the Eastern Europe (at the very end of the Late Pleistocene and in the early Holocene). The results of the ancestral area reconstruction are consistent with the hypothesis of a Middle Asian origin of the C. suaveolens/C. sibirica group, recent colonization of Inner Asia and later penetration into Eastern Europe.