Egg-Surface Bacteria Are Indirectly Associated with Oviposition Aversion in Bactrocera dorsalis

Abstract

Li et al. report that the oriental fruit fly B. dorsalis avoids oviposition on fruits that have been previously infested by conspecifics. Flies identify egg-infested fruits via increased β-caryophyllene emissions, which are induced by bacteria enriched on the egg. © 2020 Elsevier Inc.; Finding a suitable oviposition site is a challenging task for a gravid female fly, because the hatched maggots have limited mobility, making it difficult to find an alternative host. The oriental fruit fly, Bactrocera dorsalis, oviposits on many types of fruits. Maggots hatching in a fruit that is already occupied by conspecific worms will face food competition. Here, we showed that maggot-occupied fruits deter B. dorsalis oviposition and that this deterrence is based on the increased β-caryophyllene concentration in fruits. Using a combination of bacterial identification, volatile content quantification, and behavioral analyses, we demonstrated that the egg-surface bacteria of B. dorsalis, including Providencia sp. and Klebsiella sp., are responsible for this increase in the β-caryophyllene contents of host fruits. Our research shows a type of tritrophic interaction between micro-organisms, insects, and insect hosts, which will provide considerable insight into the evolution of insect behavioral responses to volatile compounds. © 2020 Elsevier Inc.