Population genetics of Japanese monkeys: III. Ancestry and differentiation of local populations

Genetic variability in local populations of the Japanese macaque (Macaca fuscata) was quantified by the proportion of polymorphic loci (P_poly) and the average heterozygosity per individual ( ) from the starch- and polyacrylamide-gel electrophoreses of blood proteins controlled by 32 independent genetic loci. P_poly averaged 13.6% and 2.1%, the values being at lower level compared with other mammalian species. Geographical distribution of the genetic variations was not uniform in the whole species but its local differentiation was remarkable. Genetic variability tended to be lower in the southern localities, especially in the southernmost island of Yaku, than in the central and northern localities. The genetic distance and the principal component analyses showed that the most divergent local populations were the population in the Shimokita peninsula at the northernmost distribution area of the species and the populations on the Yaku island at the southernmost. The most contributory loci to the genetic divergence were the PGM-II, Gc, and Hb-β, the variant allele at the first locus being concentrated in the Yaku island, in the Shimokita peninsula, and in the easternmost Boso peninsula, and the variant allele at the latter two loci having high frequencies in the Shimokita and the Izu peninsulas. The Hennigian cladistic analysis, for which the Chinese rhesus macaque (M. mulatta) was used as the outgroup, revealed that the number of presence of derived (apomorphic) alleles was conspicuously smaller in southern islet populations than in central and northern populations, whereas any areal tendency was not recognized in the number of loss of ancestral (plesiomorphic) alleles. The observed distribution pattern that the plesiomorphic variant allele at the PGM-II locus concentrated only in the peripheral (southernmost, northernmost, and easternmost) ranges of the species, would indicate, as a possibility, the occurrence of two or more waves of immigration of ancestors of the present-day Japanese macaque from the Asian continent.