Inferring the Origin of <i>Cylas formicarius</i>（Coleoptera: Brentidae）Found and Eradicated in Hamamatsu City, Shizuoka Prefecture, Using Molecular Phylogenetic Analysis

The sweet potato weevil, Cylas formicarius（Fabricius）（Coleoptera: Brentidae）, was detected in October 2022 in Hamamatsu City, Shizuoka Prefecture, Japan, with eradication completed in November 2024 through emergency pest control under the Japanese Plant Protection Act. To determine its origin, we analyzed genetic variation in the mitochondrial cytochrome c oxidase subunit I（mtCOI）gene of 2,024 individuals from 20 countries, including Japan. In total, 158 mtCOI haplotypes were identified worldwide, with 94 detected in 1,729 individuals from 47 geographical populations in Japan. A maximum likelihood phylogenetic tree revealed 11 clades（Clades A–K）, with Japanese haplotypes distributed among three clades: Clades A（Nansei Islands and Taiwan）, C（Ogasawara Islands, China, Hong Kong, Fiji, and Australia）, and J（Minamitorishima Island and the Philippines）. All 24 individuals collected from 10 sites in Hamamatsu City shared the same haplotype within Clade C. These results suggest that the invasive population of C. formicarius, which occurred in Hamamatsu City, originated from a single source, possibly the Ogasawara Islands or another country.