Abstract
The parasitoid wasps Torymus sinensis (Ts) and three strains of T. beneficus (early-spring strain: TbE; late-spring strain: TbL; autumn strain: TbA) are respectively introduced and indigenous natural enemies of the chestnut gall wasp Dryocosmus kuriphilus, an invasive chestnut pest. In this study, the genetic relationships among Ts and three strains of Tb from Japan, China and Korea were investigated by sequencing a portion of the mitochondrial cytochrome oxidase subunit I (COI) gene. Three distinct groups were recognized in a constructed phylogenetic tree, the first group further consists of three subgroups. Ts belongs to two subgroups, whereas TbL belongs to the remaining subgroup. TbE and TbA belong to the second group, indicating that TbL is genetically more closely related to Ts a different species than to TbE and TbA strains considered the same species. This requires a reconsideration, especially for TbL, of their taxonomical treatment. The third group consisted of an indigenous Torymus parasitoid that we were unable to identify morphologically, indicating that an unknown Torymus parasitoid that is both genetically and morphologically different from the Ts and the Tb strains exploits D. kuriphilus in Japan.
