Study of a contact between two chromosomally monomorphic races of Sorex araneus L. (common shrew).

One hundred and twelve specimens of the common shrew from 21 populations in NE Poland were studied from an area of contact between chromosomal race II (metacentric chromosomes: hi, ko, gm, np) and race VII (ki, hn, gr, mp). No direct contact was found between the races in the study area; there were no mixed or hybrid populations. The shortest distance between populations of the two races was 1.2-1.6 km. Possible explanations for this pattern of the races' disjunction are discussed.