2012 Program (PDF) - International Society of Chemical Ecology

Thursday 26th July, 17:15 – 17:30 hSemiochemical parsimony in Leptopilina heterotoma (Figitidea, Hymenoptera),a parasitoid of DrosophilaSTÖKL J 1 , HOFFERBERTH J 2 , PRITSCHET M 1 , BRUMMER M 1 , RÖSSLER T 1 , RUTHER J 1johannes.stoekl@biologie.uni-regensburg.de1 Institute for Zoology, Chemical Ecology Group, University of Regensburg, GERMANY2 Department of Chemistry, Kenyon College, Ohio, USAWasps of the genus Leptopilina (Figitidae, Hymenoptera) are solitary larval parasitoids ofDrosophila flies.In this study we show, that female Leptopilina heterotoma produce (-)-iridomyrmecin in acephalic gland and release it upon encounter with potential predators. Bioassays show thatiridomyrmecin has a strong repellent effect on ants and that stereoisomers of iridomyrmecindiffer in their repellent properties. Specifically, (-)-iridomyrmecin repelled the ants significantlylonger from potential food items than (+)-iridomyrmecin, (+)-isoiridomyrmecin or (-)-isoiridomyrmecin. Using headspace analyses we also show, that the wasps adjust theamount of iridomyrmecin released depending on the size of the predator.Males of L. heterotoma produce only the less effective (+)-isoiridomyrmecin for defense. Thissuggests a second possible function of iridomyrmecin in the sexual communication ofLeptopilina. In support of this hypothesis, we have now demonstrated that (-)-iridomyrmecin,in combination with some minor iridoid compounds, is an essential component of the femalesex pheromone blend that attracts males and triggers courtship behavior.Furthermore, preliminary data suggest that (-)-iridomyrmecin is also used by L. heterotomafemales as a spacing pheromone to detect and avoid host patches which are alreadyexploited by conspecific females.The threefold function of (-)-iridomyrmecin in defence, sexual communication, and host patchselection is an excellent example demonstrating the economic use of costly chemicalmessengers by insects, commonly referred to as „semiochemical parsimony‟. The fact thatpure (-)-iridomyrmecin is sufficient for chemical defence but additional minor components areessential for the sex pheromone function indicates L. heterotoma may be a prime modelorganism for the study of cue signal evolution.References1. Journal of Chemical Ecology (2012) 38: 331-33981