Olfactory Signals and Reception in a Pest Fly, Drosophila suzukii

For most insects, olfaction plays a central role in the performance of behaviors necessary for their own particular mode of survival and reproduction. As insects adapt to different environments and specialize on novel hosts, typified by unique chemical landscapes, their olfactory structures and molecular correlates diverge and adapt enabling them to locate suitable hosts, habitats, oviposition sites, and conspecifics. The study of olfaction in drosophilids, particularly the model organism Drosophila melanogaster, has greatly advanced our understanding of insect olfaction. Yet, little of what has been discovered of Drosophila olfaction has been directly translated to applied entomological problems, since Drosophila have rarely been considered direct pests of economic importance. However, the recent introduction of an East Asian vinegar fly, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), into continental North America and Europe, has changed this perspective. In contrast to D. melanogaster and the vast majority of saprophytic drosophilids which feed and oviposit on rotten fruits, D. suzukii lays eggs in ripening fruits, causing significant damage to invaded fruit-crops. Drosophila suzukii’s preference and utilization of ripening fruits represents a niche expansion that demands a variety of adaptations. This presents an opportunity to investigate olfactory signals and reception associated with D. suzukii’s novel niche exploitation in relation to other drosophilids. The research in this dissertation assesses olfactory guided behavior, investigates chemical landscape and conspecific cues, and identifies functional olfactory correlates for D. suzukii in parallel with related flies, especially D. melanogaster. Through behavioral assays and electrophysiological work on both antennae and maxillary palps, evidence is provided for a species difference in sensitivity to odorants as well as differential odor resolution between D. suzukii and D. melanogaster. Furthermore, a full investigation of cuticular hydrocarbon profiles, compounds critical in conspecific communication, from four closely related drosophilids demonstrates species variations, likely affecting conspecific signaling. This research has the potential to aid in the development of agricultural tools for D. suzukii’s management in addition to contributing to our understanding of the role olfaction plays in novel niche utilization.