Invasion pathway and potential risks of a bamboo-nesting carpenter bee, Xylocopa tranquebarorum (Hymenoptera: Apidae), and its micro-associated mite introduced into Japan

Despite plant quarantine systems, many organisms have been unintentionally introduced by the rapid expansion of international trade. Xylocopa tranquebarorum, a large species of carpenter bee that nests in bamboo shoots, was introduced into Japan approximately 5 years ago and, along with its specifically associated mite, has established populations in Toyota and Nagoya in Aichi Prefecture and Anpachi in Gifu Prefecture. Because X. tranquebarorum only nests in dead bamboo shoots and because its associated mite differs from the mite species associated with X. tranquebarorum in Taiwan but is morphologically similar to the species described in India, Indonesia, and China, we suspect that X. tranquebarorum and its mite were introduced via processed bamboo shoots from continental Asia. Because the most probable pathway of associated microorganisms is host introduction, biological and ecological information, such as an inventory of symbionts, is crucial to avoid the risk of invasive symbiotic microorganisms. Although X tranquebarorum may become a pest in the bamboo industry if its distribution is expanded by human transport, its associated mite is suspected to be of low risk as house dust but to have a high contamination risk for the Japanese endemic mite, Sennertia alfkeni, associated with native Japanese carpenter bees.