Population genetic structure and implications for natal philopatry of nesting green turtles Chelonia mydas in the Yaeyama Islands, Japan

摘要

Patterns of mitochondrial DNA (mtDNA) variation and microsatellite genotyping were used to analyze the population genetic structure of nesting green turtles Chelonia mydas (n = 67) in the Yaeyama Islands of Japan, which represent the northern limit of green turtle nesting in the west-ern Pacific Ocean. The composition of a mixture of 6 mtDNA haplotypes from 3 rookeries, southwest-ern (SW) Iriomote Island (n = 26), eastern (E) Ishigaki Island (n = 29), and northwestern (NW) Ishigaki Island (n = 12), produced genetic diversity values (haplotype diversity h = 0.582 to 0.638, nucleotide diversity it = 0.0138 to 0.0244) within the high end of the range found in previous studies. The phy-logeny of haplotypes, representing 3 distinct clades, indicated historical introgressions by individuals with divergent haplotypes from both Pacific colonies and Indian and Southeast Asian colonies. Sig-nificant genetic differentiation, at least between SW Iriomote Island and Ishigaki Island in which samples from E and NW Ishigaki were combined, was observed based on mtDNA; this indicated pre-cise female natal philopatry compared to other Pacific and Indian regions, although microsatellite analyses of 4 markers revealed no significant genetic differentiation. Further studies are needed to clarify the precision of natal philopatry and male-mediated gene flow; however, this study provides valuable insights about the phylogeography of green turtles in Japan. Our results also underscore the need for green turtle conservation in the northwest Pacific Ocean.