Natural hybridization between extremely divergent chromosomal races of the common shrew (Sorex araneus, Soricidae, Soricomorpha): hybrid zone in Siberia

摘要: Chromosomal races of the common shrew differ in sets of metacentric chromosomes and on contact may produce hybrids with extraordinarily complex configurations at meiosis I that are associated with reduced fertility. There is an expectation that these may be some of the most extreme tension zones available for study and therefore are of interest as potential sites for reproductive isolation. Here, we analyse one of these zones, between the Novosibirsk race (characterized by metacentrics go, hn, ik, jl, mp and qr) and the Tomsk race (metacentrics gk, hi, jl and mn and acrocentrics o, p, q and r), which form hybrids with a chain‐of‐nine (CIX) and a chain‐of‐three (CIII) configuration at meiosis I. At the Novosibirsk–Tomsk hybrid zone, the CIX chromosomes form clines of 8.53 km standardized width on average, whereas the cline for the CIII chromosomes was 52.83 km wide. The difference in these cline widths …