Abstract
Restriction fragment variations in nuclear ribosomal DNA (rDNA) spacers, and in mitochondrial DNA (mtDNA), were examined in a total of 14 individuals of the two Korean subspecies of the striped field mouse : Apodemus agrarius coreae, collected from the mainland and Jindo and Geoje islands, and A. a. chejuensis collected from Cheju Island. Analysis of heterogeneity in rDNA spacers with ten restriction enzymes, showed that the main Korean populations of A. a. coreae have a similar genetic background irrespective of their geographic locality. In the population from Cheju Island, however, an accumulation of a specific variation, a new SacI site within the internal spacer region of rDNA, was observed. In the contrast, analysis of heterogeneity of mtDNA with ten restriction enzymes, revealed that mtDNA haplotypes from the offshore islands were distinct from one another and distinct from those of the mainland, with up to 4% of sequence divergence, which corresponds to 1-2 million years of divergence time. It is suggested that certain geographic conditions, such as the existence of a large number of small islands, may help preserve various mtDNA haplotypes which diverged many millenial ago.
