Abstracts - Deutsche Zoologische Gesellschaft

Ecology Symposium 55O EC.5 (Sa) - ENQuantification of pollinator footprints on natural flowers: a tool for pollinationecologistsSebastian Witjes, Thomas EltzInstitut Neurobiologie, AG Sinnesökologie, Universität DüsseldorfObservational assessment of pollinator identity and visitation frequency at flowering plants is timeconsuming, especially when flower visitor abundance is low. As an alternative, we propose to reconstructpast visitation by extracting and quantifying visitor footprints on flower corollas by meansof GC/MS. We used bumblebee pollinated plants and their pollinators as model organisms. Thecuticle of bumblebees (as of many other insects) is covered by a mixture of long chained alkenes andalkanes. During flower visits traces of these cuticular hydrocarbons remain on visited flower corollas.The deposited alkenes (C21 to 31) do not occur on unvisited flowers, are of very low volatilityand partly specific to certain bumblebee species. Our results show that after visits such bumblebeealkenes accumulate linearly on flower corollas with increasing numbers of visits, and are retainedalmost without loss for up to 24 hours. In laboratory experiments we could show that there was noeffect of ambient temperature (15° or 25°C treatment) on the amount of bumblebee alkenes retainedon visited corollas. This suggests that residual footprint quantification is informative under a rangeof environmental conditions. Upcoming experiments will show whether species-specific markeralkenesallow a proportional assignment of visits to different bumblebee species in the visitor community.O EC.6 (Sa) - ENElectrophysiological study of pine volatile perception by a parasitoid of pine sawflyeggsIvo Beyaert, Nicole Wäschke, Monika Hilker1Institut für Biologie, Freie Universität BerlinEgg deposition by the pine sawfly Diprion pini on Scots pine (Pinus sylvestris) is known to inducerelease of pine volatiles that attract the egg parasitoid Chrysonotomyia ruforum. The attractive oviposition-inducedpine odour consists of numerous terpenoid compounds and differs from non-attractivepine odour especially by enhanced quantities of (E)-β-farnesene. Behavioral bioassays revealedthat this sesquiterpene is attractive to C. ruforum only when offered at the background of non-attractivepine odour. These previous results suggest that the egg parasitoid is attracted to ovipositioninducedpine when a specific ratio of (E)-β-farnesene and other pine volatiles is released. However,which of the numerous “other pine volatiles” are relevant for attraction of C. ruforum? To approachthis question we recorded electroantennogram (EAG) responses by female C. ruforum to six monoterpenesand six sesquiterpenes. These compounds were selected based on their chemical structureand abundance in attractive oviposition-induced pine odour. The following components elicited aresponse significantly different from the response to the solvent: the monoterpenes 3-carene, β-phellandrene and (E/Z)-β-ocimene, as well as the sesquiterpenes α-copaene, (E)-β-caryophyllene,α-humulene and (E)-β-farnesene. The electrophysiological results will be discussed with respect tothe behavioural studies on the attractiveness of oviposition-induced pine odour.