Genetic differentiation in Sorex

Frykman, I. and Bengtsson, B.O. 1984. Genetic differentlation in Sorex. III. Electrophoretic analysis of a hybrid zone between two karyotypic races in Sorex araneus. —Hereditas 100:259–270. Lund, Sweden. ISSN 0018–0661. Received January 26, 1984 A karyotypic hybrid zone in the common shrew. Sorex araneus L., has been electrophoretically analyzed. In the investigation, we have used 291 animals representing eight populations from a region in the north of Sweden where the central and the northern karyotypic races come into contact. Chromosomal analysis has shown that three of the populations belong to the northern race and four to the central race, while one population was found to contain karyotypic hybrids and also animals of both chromosomal types. The changes in allele frequencies over the hybrid zone have been analyzed for three genetically variable enzyme loci, Ada, EsBI and Mpi. The clines shown by the Mpi A, B and C alleles over the investigated region indicate that gene flow occurs between the two karyotypic races. This conclusion i also supported by the finding of ten out of eleven alleles from the three investigated loci in animals belonging to both races. The genetic exchange appears to go in both directiona, but has not been sufficient to equalize the allele frequencies between the populations in the contact region. The idea that populations with different distances to the karyotypic hybrid zone contain different admixtures of two original gene pools, one coming from the central karyotypic race and the other from the northern race. is shown to be consistent with data obtained for the informative Mpi alleles.