Relationship among local populations of the white grub beetle, Dasylepida ishigakiensis (Coleoptera: Scarabaeidae), detected by phylogenetic analysis based on the mitochondrial DNA sequence

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The white grub beetle Dasylepida ishigakiensis is distributed in the southwestern part of the Ryukyu Islands of Japan. In addition to the three previously recognized local populations occurring in natural forests of Iriomote-jima and Ishigaki-jima Islands, and sugarcane fields in the Miyako region, including Miyako-jima and Irabu-jima Islands, a new population was collected from farmland on Ishigaki-jima in January 2007 and 2008. In order to examine the relationships among these populations, we performed molecular phylogenetic analysis of 150 individuals based on the sequences of two mitochondrial DNA fragments (1.9 kb in total length), one containing a portion of the cytochrome oxidase subunit I gene and the other containing a portion of the 16S rRNA gene. As a result, individuals were clearly divided into six haplotypic groups. The newly discovered Ishigaki-jima population contained three haplotypic groups, two of which were specific to this population and the third of which was the same as one of the two haplotypic groups detected from the Miyako region, indicating insect movement between Ishigaki-jima and the Miyako region. Based on these results, we discuss the direction of insect dispersal in conjunction with the evolutionary history of insular populations of this species.