Biological and genetic diversity of colonizing and endemic species of Drosophila in the Ogasawara Islands

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Faunal and seasonal surveys on drosophilid flies by banana-trapping and net sweeping were carried out in the Ogasawara Islands on July 2009, December 2009 and May 2010. A total 116, 857 individuals of 22 species including 9 endemic species were collected at the seven and five collection sites of Chichijima and Hahajima, respectively. In the both islands, Drosophila hypocausta, recently colonizing species, was the most abundant on July of 2009. On the other hand, D. simulans in Chichijima and D. pectinifera in Hahajima were the most dominant species in the collection of December 2009 and May 2010. The present survey showed recent increase of D. hypocausta and D. suzukii in the Ogasawara Islands, but the endemic species such as D. pectinifera were collected more than those of the previous surveys, indicating increasing of biodiversity of drosophilid fauna. Genetic diversity and differentiation of mitochondrial DNA genes, COI and COII, were studied using three endemic species(D. pectinifera, Dichaetophora ogasawarensis, Scaptomyza hexasticha) and three colonizing species(D. hypocausta, D. suzukii, D. kikkawai). Genetic diversities of the three endemic species and D. hypocausta were larger than those of the other colonizing species. Haplotype analyses of mitochondrial DNA suggested that immigration of the colonizing species occurred from Chichijima to Hahajima. In addition, genetic properties of the endemic species are different between Chichijima and Hahajima, suggesting the importance of the protection of populations in each island.