Evolutionary significance of admixture and fragmentation of Sika Deer populations in Japan

Abstract

The sika deer is genetically very close to the red deer (Cervus elaphus): nucleotide divergences between the two species are less than 1% in most of the protein-coding sequences. Genetic markers that were developed for red deer and other cervine, ovine, and bovine species are readily applicable to genetic analyses of sika deer. By using such DNA markers, I and my colleagues studied the level of genetic diversity of local populations, past demographic changes of populations, and spatial structures of populations. A phylogenetic tree constructed from micro satellite allele frequencies separates northern and southern groups in different clusters, showing a similar split pattern between the two lineages as observed in the mtDNA-based phylogenetic tree. However, the level of differentiation between the northern and southern mtDNA groups is lower than that among the populations in Honshu, which suggest that the genetic difference between the two groups has been reduced by the admixture. The genetic differentiation among populations was caused by a loss of genetic variation during past fragmentation of populations and not by the accumulation of novel mutations in each population. Two cases of the fragmentation of sika deer populations at a local scale, which were revealed by DNA analyses, are described in this chapter. Population genetic studies thus provide empirical data for monitoring and predicting long-term changes in demog raphy and population structure of sika deer.