The genetic relationships of two subspecies of striped field mice, Apodemus agrarius coreae and Apodemus agrarius chejuensis

We obtained 282 base pairs of sequence for the mitochondrial control region of 70 individuals of Korean striped field mice Apodemus agrarius coreae an d Apodemus agrarius chejuensis to determine the levels of genetic divergenc e between these morphologically distinct taxa. The DNA sequences showed mor e genetic diversity (pi) in A. agrarius coreae (2.98%) than in A. agrarius chejuensis (1.86%). Our data do not support the current concept that the tw o morphotypes are different species, but phylogenetic analysis indicates th at animals of A. agrarius coreae with large body size from Wan Island clust er with the large-bodied A. agrarius chejuensis, and should be included in that taxon. As currently accepted A. agrarius coreae is not strictly monoph yletic, because the large-bodied samples cluster within the range of mitoch ondrial variation of A. agrarius chejuensis. The fact that the two morphoty pes do not share mitochondrial haplotypes (chi(2) = 66, P < 0.001) suggests that there is little gene flow between them. A molecular clock estimate su ggests that the two subspecies might have been isolated at the time of sepa ration of the islands from the mainland.