The Evolution of Pheromone Communication in the Genus Leptopilina (Hymenoptera: Figitidae), a Parasitoid of Drosophila.
Final Report Abstract
Chemical communication is arguably the oldest form of communication. However, the origin and evolution of pheromones is one of the major questions in chemical ecology. Current evolutionary theory predicts that pheromones may evolve from compounds already in use for non-communicative functions. In the preceding project we found support for this hypothesis in the parasitoid wasp Leptopilina heterotoma (Hymenoptera, Figitidae), a larval parasitoid of Drosophila. We could show that females of L. heterotoma produce a defensive secretion containing iridoid compounds to defend themselves against predators. Furthermore, females of L. heterotoma use the same secretion as a chemical cue to avoid host patches already exploited by con- and heterospecific females. And finally, the females use the defensive secretion also as their sex pheromone to attract males. Other species of the genus, like L. boulardi and L. victoriae also produce a defensive secretion containing iridoid compounds. However, only in L. boulardi the iridoids are also part of the female sex pheromone (in combination with cuticular hydrocarbons, CHCs), while the female sex pheromone of L. victoriae consist of only CHCs. The aim of the proposal was to use the genus Leptopilina as a model system to study the evolution of chemical communication. Using a comparative approach, we investigated the use of iridoids as defensive allomone, chemical cue to avoid competition among females, and female sex pheromone in four more species of Leptopilina (L. clavipes, L. japonica, L. pacifica, and L. ryukyuensis) and one outgroup species. We could show that all investigated species of Leptopilina produce a defensive secretion containing iridoid compounds. However, only L. japonica also uses the iridoid compounds as female sex pheromone while in the remaining three species the CHCs are sufficient to trigger the courtship behavior in males. One factor that could explain the high chemical diversity in the composition of the female sex pheromone in the genus Leptopilina is the dispersal behavior of the wasps after emergence. We could show that in species with volatile sex pheromones consisting of iridoid compounds (L. heterotoma and L. japonica), a higher proportion of males leave the host patch before the emergence of the females than in species with low volatile sex pheromone consisting of CHCs (L. pacifica and L. ryukyuensis). Best to our knowledge, this is the first time that the volatility of female sex pheromones has been associated with the dispersal behavior of males. Our data significantly contributed to our understanding of the evolutionary origins of pheromones and revealed so far neglected evolutionary forces, like the dispersal behavior, that drive species divergence in sex pheromone composition.
Publications
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(2016) Morphology and ultrastructure of the allomone and sex-pheromone producing mandibular gland of the parasitoid wasp Leptopilina heterotoma (Hymenoptera: Figitidae). Arthropod Struct Dev 45:333–340
Stökl J and Herzner G
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(2017) Beyond cuticular hydrocarbons: chemically mediated mate recognition in the subsocial burying beetle Nicrophorus vespilloides . J Chem Ecol 43:84–93
Keppner EM, Prang M, Engel KC, Ayasse M, Stökl J and Steiger S
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(2017) Evolutionary origin of insect pheromones. Curr Opin Insect Sci 24:36– 42
Stökl J and Steiger S
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Environmentally sustainable pest control options for Drosophila suzukii. J Appl Entomol 28:873
Schetelig MF, Lee K-Z, Otto S, Talmann L, Stökl J, Degenkolb T, Vilcinskas A and Halitschke R
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Pheromones involved in insect parental care and family life. Curr Opin Insect Sci 24:89–95
Steiger S and Stökl J
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(2018) Interference of chemical defence and sexual communication can shape the evolution of chemical signals. Sci Rep 8:970. doi: 10.1038/s41598- 017-18376-w
Pfeiffer L, Ruther J, Hofferberth J and Stökl J
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(2018) Pheromones regulating reproduction in subsocial beetles: insights with references to eusocial insects. J Chem Ecol 44:785–795
Steiger S and Stökl J
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(2019) Semiochemicals mediating defense, intraspecific competition, and mate finding in Leptopilina ryukyuensis and L. japonica (Hymenoptera: Figitidae), Parasitoids of Drosophila. J Chem Ecol 45:241–252
Böttinger LC, Hofferberth J, Ruther J and Stökl J
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(2020) Dispersal from natal patch correlates with the volatility of female sex pheromones in parasitoid wasps. Front Ecol Evol 8
Böttinger LC and Stökl J
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(2020) Mate attraction, chemical defense, and competition avoidance in the parasitoid wasp Leptopilina pacifica. Chemoecology
Böttinger LC, Hüftlein F and Stökl J
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(2021) The preference of Trichopria drosophilae for pupae of Drosophila suzukii is independent of host size. Sci Rep 11:995
Häussling BJM, Lienenlüke J and Stökl J
