A HYBRID ZONE BETWEEN THE ULM AND DRNHOLEC KARYOTYPIC RACES OF SOREX-ARANEUS IN THE CZECH-REPUBLIC

The hybrid zone between the Ulm (2Na = 24; gm, hi, jl, k, n, o, p, q, r) and Drnholec (2Na = 20; gm, hi, jl, ko, nr, p, q) karotypic races w as studied in the Czech Republic. The zone of polymorphism was located at the Ceskomoravska vysocina (Bohemian-Moravian Highlands), and its width was estimated at several tens of kilometers. All the expected ka ryotypic variants were found at three highly polymorphic sites within the hybrid zone. The frequency of the ko and nr metacentrics varied am ong the samples but no deviations from the Hardy-Weinberg expectations were observed. The results obtained indicate that there is free gene flow between the hybridising races and suggest a lack of strong select ion against the hybrids.