Abstract
Restriction fragment length polymorphisms (RFLPs) in nuclear ribosomal DNA (rDNA) spacers and mitochondrial DNA (mtDNA) were examined in red-backed voles collected in Hokkaido (Japan), and Korea. These voles have been classified into six species on the basis of morphological characteristics, such as dental morphology. The RFLPs of the rDNA allowed us to classify the voles into three distinct groups : rCrt (Clethrionomys rutilus), rCrf (C. rufocanus, C. sikotanensis and Eothenomys regulus) and rCrx (C. rex and C. montanus). The estimated sequence divergence between rCrt and rCrf and that between rCrf and rCrx were 4.8% and 2.3%, respectively. In the rCrf group, no major differences in mtDNA were observed among the populations from the mainland of Hokkaido, Rishiri Island, and Daikoku Islet. Similarly, in the rCrx group, mtDNA haplotypes from the mainland of Hokkaido and Rishiri I. were closely related each other, indicating that there have been genetic exchanges between the populations after speciation, or those haplotypes are derived from recent common origin. The Korean red-backed vole, which is sometimes referred to E. regulus, had rDNA identical to that of the rCrf group from Hokkaido. By contrast, the mtDNA haplotype of the Korean vole was substantially different from that of C. rufocanus in Hokkaido (8% sequence divergence). These results imply that the Korean red-backed vole and C. rufocanus in Hokkaido are very closely related and that ancestrally diverged mtDNA haplotypes have been maintained in the different geographic regions.
