Mitochondrial DNA variation in Brontispa longissima (Coleoptera: Chrysomelidae)

The coconut hispine beetle, Brontispa longissima (Gestro), is a serious invasive pest of the coconut palm Cocos nucifera L. in Southeast Asia and the Pacific region. The beetle is believed to be native to Papua New Guinea (PNG) and Indonesia. Since the late 1930s, it has invaded Pacific islands such as Vanuatu, Tahiti and Samoa. In the late 1990s, the beetle was found in the Mekong Delta in Vietnam and in the Maldives; it has now spread to Southeast and East Asian countries, and outbreaks have been reported in these places on C. nucifera. Invasion by B. longissima is of great concern, and the beetle is listed in the Global Invasive Species Database (2010). To study genetic variation and determine the area of origin of B. longissima, we conducted molecular phylogenic analysis using mitochondrial cytochrome oxidase subunit I (COI) genes of specimens collected from several localities. The results showed that there are two monophyletic groups: One group is distributed in rather limited area (Australia, PNG, Samoa, and Sumba Island), whereas the other group is collected from wide area including both Asia and Pacific region. Biological traits were distinct between the groups, including egg production, body size, and development time. The inter-group crosses produced significantly fewer progeny than intra-group crosses. These results suggest that B. longissima. contains two cryptic species. Invasive ability and current distribution of the two groups were also discussed.