Genetic divergence among populations of the white grub beetle, Dasylepida ishigakiensis (Coleoptera: Scarabaeidae), distributed in the southern part of the Ryukyu Islands of Japan, detected from mitochondrial DNA sequences

Abstract

The white grub beetle, Dasylepida ishigakiensis, was originally known only in the Yaeyama region, including Ishigaki-jima and Iriomote-jima Islands, of the southern part of the Ryukyu Islands, Japan. At the end of the 1990s, a population was discovered to occur abundantly in sugarcane fields in the Miyako region, including Miyako-jima and Irabu-jima Islands, approximately 90 km northeast of the Yaeyama region. Using specimens collected from these islands, fragments of mitochondrial DNA containing portions of ribosomal RNA, cytochrome c oxidase subunit I, and cytochrome b genes were sequenced. Phylogenetic analyses using the sequences revealed discrete separation into three clades: two comprised exclusively of individuals from Ishigaki-jima and Iriomote-jima, respectively, and the third comprised of individuals from the Miyako region, including both Miyako-jima and Irabu-jima. Separation of the clades by rather long branches suggested that they have been geographically isolated for an evolutionarily long period and indicated that the population in the Miyako region was not established by the recent invasion of insects from the Yaeyama region.

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

“…Comparison of sequences obtained in this and our previous study (Muraji et al, 2008a) confirmed that haplotypic groups A1ϩA2, B2, and C corresponded to three previously reported local populations, the Miyako population, the Ishigaki-jima natural forest population, and the Iriomote-jima population, respectively. Two others, Subgroups A3 and B1, were specific to the newly discovered Ishigaki-jima population collected on farmlands in January 2008.…”

“…Commercially purchased (R)-2-butanol was used as an attractant. All other specimens were collected as described in Muraji et Two mtDNA fragments, one containing a portion of the cytochrome oxydase subunit I gene (COI) and the other containing a portion of the 16S ribosomal RNA gene (rDNA), were amplified and sequenced for all 150 individuals according to the methods described in Muraji et al (2008a), except that primer 12Rb was not used in this study. Sequences obtained from representative individuals were submitted to DDBJ/EMBL/GenBank nucleotide sequence databases (Accession numbers: AB499094-AB499121).…”

“…Nucleotide sequences were aligned as described in Muraji et al (2008a) and used to compute basic statistical data and to generate phylogenetic trees based on the neighbor-joining method by MEGA ver. 3.1 software (Kumar et al, 2004).…”

“…Because the Miyako and Yaeyama populations have different habitats and larval food habits, and the adult males have several different morphological and chemical features, they were suggested to be different subspecies or species (Fujioka, 2001;Hirai et al, 2008). Muraji et al (2008a) found that nucleotide sequences of the mitochondrial DNA (mtDNA) were distinct among populations of Ishigaki-jima, Iriomote-jima, and the Miyako region. Based on these results, Muraji et al (2008a) On the other hand, Nakata and Nakata (2006) discovered a new population occurring in the farmlands of Ishigaki-jima.…”

“…Muraji et al (2008a) found that nucleotide sequences of the mitochondrial DNA (mtDNA) were distinct among populations of Ishigaki-jima, Iriomote-jima, and the Miyako region. Based on these results, Muraji et al (2008a) On the other hand, Nakata and Nakata (2006) discovered a new population occurring in the farmlands of Ishigaki-jima. We also collected a small number of adults of this population in January 2007.…”