Genetic Analysis of Invasive Rats From the Hahajima Islands in the Ogasawara Islands

ABSTRACT

Based on mitochondrial DNA (mtDNA) sequences, we concluded that the Hahajima Islands are largely inhabited by Rattus norvegicus (brown rat), except for Katsuodorijima. The previous study reported that the Chichijima Islands were occupied by Rattus rattus complex (RrC) (black rats). We considered that R. norvegicus inhabits the Hahajima Islands owing to a combination of factors, such as climatic differences between the Chichijima Islands and the Hahajima Islands, the timing of the invasion by invasive rodents in the satellite islands of Hahajima, and geographical factors. Based on a comparative analysis of the Chichijima individual of RrC, we concluded that RrC II (corresponding to Rattus tanezumi ) inhabits Katsuodorijima. The previous study reported that RrC II inhabits Hahajima; therefore, we considered that RrC II migrated from Hahajima to Katsuodorijima by swimming because Katsuodorijima is geographically adjacent to Hahajima and can be reached by swimming. In this study, unique haplotypes (CT6, CT8, and TC7) in R. norvegicus at Meijima and Mukohjima, based on the D‐loop analysis, were observed. To the best of our knowledge, these unique haplotypes have not been reported in previous studies; therefore, we considered that these haplotypes originated on Mukohjima and Meijima. Based on this result, although the use of mtDNA data to demonstrate whether migration occurred would be difficult, we suggested that R. norvegicus likely did not migrate from Meijima or Mukohjima to other islands. Invasive rodents severely affect the ecosystems of the Ogasawara Islands, including the Hahajima Islands. Predation of Ogasawara Greenfinch ( Chloris kittlitzi ) nests is a representative problem. This study provides helpful information for promoting effective invasive rodent control on the Hahajima Islands.