Genetic variation of two weevil pests of sweet potato, Cylas formicarius (Coleoptera: Brentidae) and Euscepes postfasciatus (Coleoptera: Curculionidae), in Japan based on mitochondrial DNA

We examined the genetic variation in the sequences of cytochrome c oxidase subunit I gene (DNA barcode region) and some other regions of mitochondrial DNA of sweet potato weevil, Cylas formicarius (Fabricius, 1798) (Coleoptera: Brentidae), and West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire, 1849) (Coleoptera: Curculionidae), in Japan. In the DNA barcode region of C. formicarius , 139 haplotypes were detected from 1705 individuals belonging to 46 geographical populations. In the maximum likelihood phylogenetic tree, haplotypes found in Japan were mainly divided into three clades. In the DNA barcode region of E. postfasciatus , two haplotypes were detected from 82 individuals belonging to eight geographical populations. Of those haplotypes, Hap 1 was detected from the Nansei Islands, Fiji, Samoa, and Tonga, while Hap 2 was detected from the Nansei Islands and Samoa. These results suggest that the Japanese populations of both the species were derived from several foreign countries. Based on the haplotype network analyses of some other gene regions, those regions may be useful for a more detailed estimation of the origin of an accidentally collected individual in non-distribution area in Japan.