The Combined Use of an Attractive and a Repellent Sex Pheromonal Component by a Gregarious Parasitoid
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Gregarious parasitoids usually clump their cocoons together and the adults emerge in a synchronized fashion. This makes it easy for them to find mating partners and most copulations indeed take place at the natal patch. Yet, males should leave such sites when females are no longer receptive. As yet, this decision-making process and the possible involvement of pheromones were poorly understood. Here we report on a remarkable use of attractive and repellent pheromones of the well-studied gregarious parasitoid species Cotesia glomerata (L.) (Hymenoptera: Braconidae). Virgin C. glomerata females were found to release an attractive as well as a repellent compound, which in combination arrest males on the natal patch, but after mating the females stop the production of the attractant and the males are repelled. The repellent compound was identified as heptanal, which was also released by males, probably reducing male-male competition on the natal patch. We also confirmed that the sex ratio of the emerging wasps can vary considerably among patches, depending on the relative quality of hosts and the number of females that parasitize a host. The newly revealed use of attractive and repellent pheromone compounds by C. glomerata possibly helps maximize mating success under these variable conditions.
KeywordsSex pheromones Parasitoids Mate location Sex allocation Cotesia glomerata
We would like to thank Prof. Joachim Ruther from University of Regensburg, Germany, who provided valuable comments on an early version of manuscript. We thank Radu Slobodeanu from Institute of Mathematics, University of Neuchâtel, for the help with the statistics. Gaylord Desurmont, Huijuan Guo, Apostolos Kapranas and Armelle Vallat gave suggestions for the experimental designs or chemical analyses. The research was funded by China Scholarship Council, No: 201206300090 (HX), the Outstanding Young Scholars Fund of ZAFU, No: 2034070001 (GZ) and National Natural Science Foundation of China, No: 31572020 (GZ).
H.X., G.Z., S.D., T.D. and T.T. designed experiments; and H.X. and G.Z. performed bioassays. I.S., S.D., M.V.A., G.Z., L.C., and H.X. performed the electrophysiological analyses. H.X., G.Z., L.C. and G.R. did fractionation and chemical analyses. H.X. analysed data and made the Figs. H.X., T.D. and T.T. wrote an early version of manuscript. All authors commented on the manuscript.
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Conflict of Interest
The authors declare that they have no conflict of interest.
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