Genetic Assessment on the Origin of Alien Macaques in the Boso Peninsula in Japan

Japanese macaques and alien macaques have hybridized in the Boso Peninsula, Chiba Prefecture, Japan. In this study, the origin of the alien species was investigated by molecular assessments with mitochondrial DNA (mtDNA) and Y-chromosome genes. Maternal origin was assessed by comparing mtDNA sequence records. The results suggested that the alien species in the southern part of peninsula originated from the rhesus macaques in eastern China. Y-chromosome assessments with three microsatellite (Y-STR) loci detected a unique haplotype that is distributed in Japanese macaque habitats. Its origin was assessed by the TSPY (testis-specific protein on Y-chromosome) gene, suggesting the possibility of the involvement of long-tailed macaques in the Indochina region or rhesus macaques different from known source. Further investigation of historical documents and interviews disclosed the existence of a facility of long-tailed macaques planned for vaccine production in the past. This study presented novel evidence that the hybridization of Japanese macaques in the Boso Peninsula has the possibility to associate not only with rhesus macaques, but also with long-tailed macaques from the Indochina region. It is important to further monitor the status of Japanese macaques and changes in their hybridization in the peninsula for future conservation purposes.