GENETIC DIFFERENTIATION AND PHYLOGENETIC- RELATIONSHIPS AMONG PALEARCTIC MICE (RODENTIA, MURIDAE)

Genetic differentiation of 18 Palearctic mouse species (genera Sylvaem us, Mus, Apodemus, Micromys, and Rattus) with respect to 31 biochemica l loci was estimated to define the taxonomic status of these genera. O n the basis of genetic data, two independent centers of origin of spec ies belonging to the family Muridae were identified. The first is the Indo-African center, from which the modern Sylvaemus species and Palea rctic representatives of Mus originated in the Pleistocene (1.0-2.0 mi llion years ago), Genera Micromys and Apodemus, which diverged in earl y Pliocene (about 7 million years ago), trace their origin to the same center. From the second center, located in Southeast Asia, Rattus spe cies radiated. The genetic divergence of taxa issuing from these two c enters attains the level characteristic of differentiation between fam ilies and dates back to the late Miocene (over 10 million years ago), Species were compared, pairwise to determine the percent of fixed gene differences (Pfd) between them, Analysis of Pfd distribution confirme d distinct periodicity of speciation in mice and revealed two speciati on peaks. The first, al the level of genera, occurred in the Pliocene, and the second, at the species level, in the Pleistocene.