To understand the maintaining genetic diversity is very important for conservation. In ecological time scale, gene flow and genetic drift change genetic diversity. We study about the maintaining genetic diversity based on effective population size. The magnitude of genetic drift depends on effective population size. Even if effective population size is same, there is difference of the number of genes which are inherited to next generations between mtDNA and nDNA. So, we made comparison between its.

In this study, we used the D-loop region and microsatellites to investigate the genetic diversity of 673 individuals in 37 populations of Myodes rufocanus. The relationship between genetic diversity and area of island showed significance. However the comparison in genetic diversity did not show significant differences among groups which were divided by difference of population fluctuation pattern and mean density. Because mtDNA showed very high genetic diversity, we made simulation. It suggested the importance of male-biased dispersal and different genetic structure between sexes. Then, the relationship between genetic diversity and the proportion of males showed significance.