Tectonics of the Ryukyu Island Arc

Hirai

Akino

et al. 2008

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.

Section: Discussionmentioning

confidence: 99%

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

Hirai

Akino

et al. 2008

“…Thus, the Iriomote-jima population must have long been separated from other populations during their evolutionary history. Iriomote-jima is only 16 km from Ishigaki-jima, and paleogeographic studies have postulated that these islands were connected several times by paleo-lands in the Pleistocene (Kizaki and Oshiro, 1980;Ota, 1998;Kimura, 2002). Thus, this species has never crossed the short distance between Iriomote-jima and Ishigaki-jima, irrespective of whether these islands were separated by open sea.…”

Section: Discussionmentioning

confidence: 99%

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

Hirai

Akino

et al. 2010

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.

“…For the land configuration in the late Pleistocene, Kizaki and Oshiro (1980) postulated the emergence of several large islands connecting neighboring islands. Lin et al (2002) suggested the presence of three or four large islands approximately corresponding to the Amami, Okinawa, and Sakishima regions (Sakishima indicates the southwestern Ryukyu Islands, including both the Miyako and Yaeyama regions) based on molecular analyses of grass lizards.…”

Section: Discussionmentioning

confidence: 99%

Genetic variation of the green chafer, Anomala albopilosa (Hope) (Coleoptera: Scarabaeidae), in the Ryukyu Islands of Japan detected by mitochondrial DNA sequences

Arakaki

Ohno

et al. 2008

In the Ryukyu Islands of Japan, larvae of the green chafer Anomala albopilosa (Hope) are known as a serious pest of sugarcane. Based on sequences of mitochondrial ribosomal RNA genes obtained from specimens collected in this and adjacent areas, the phylogenetic relationships among local populations and geographic distribution patterns of haplotypic groups were examined. As a result, individuals were divided into five groups of haplotypes (Groups A-E). The shape of the phylogenetic trees suggested that they have been separated for a long period in their evolutionary history. Among the three groups distributed in the Ryukyu Islands, Groups B and D were restricted to the northern Amami region and Yaeyama region, respectively, while the range of Group C extended from the Amami to Yaeyama regions through the Okinawa and Miyako regions and largely overlapped the other two groups. This result was considered to suggest that the insular populations of this species were genetically muddled by the recent expansion of Group C that probably originated in the Okinawa region in the central Ryukyu Islands. Causes of these phenomena are discussed in relation to the food habits of this species and the paleogeography of this area.