Surveys of the ant faunas at ports of Tokyo Bay and the Ogasawara Islands

Abstract

Species native to oceanic islands are highly sensitive to the ecological impacts of invasive alien species, especially ants. The Ogasawara (Bonin) Islands are located approximately 1000 km south of mainland Japan and have a characteristic insular ecosystem. The risk of ecological harm via human and cargo transportation has increased as the number of tourists visiting the islands has grown since their designation as a World Natural Heritage Site. To evaluate the risk of biological invasion, we surveyed the ant faunas at ports of Tokyo Bay on the Japanese mainland and the Ogasawara Islands using sticky traps baited with honey and tuna. Our findings indicated that ant species composition was remarkably different between the ports of Tokyo and Ogasawara, and potential alien species were detected in both areas. The baited traps were likely to be more attractive than the non-baited traps, but need to be improved in future research. In particular, this is the first study to detect the invasive big-headed ant Pheidole megacephala (Fabricius) in mainland Japan, which likely arrived from Ogasawara via an ocean liner. Our study demonstrates the importance of periodically monitoring around ports to detect alien ants during the early invasion stage, when control and eradication methods are more effective.