Mate attraction, chemical defense, and competition avoidance in the parasitoid wasp Leptopilina pacifica
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CHEMOECOLOGY
ORIGINAL ARTICLE
Mate attraction, chemical defense, and competition avoidance in the parasitoid wasp Leptopilina pacifica Lea C. Böttinger1 · Frederic Hüftlein1 · Johannes Stökl1 Received: 17 March 2020 / Accepted: 27 October 2020 © The Author(s) 2020, corrected publication 2020
Abstract A major hypothesis for the evolution of chemical signals is that pheromones arise from non-communicative precursor compounds. However, data supporting this hypothesis are rare, primarily because the original functions of the antecedent compounds often have been lost. A notable exception, however, is the parasitoid wasp species Leptopilina heterotoma, whose compound (−)-iridomyrmecin is used as a defensive secretion, a cue for females to avoid competition with con- and heterospecific females, and as the primary component of the females’ sex pheromone. To better understand the evolution of sex pheromones from defensive compounds, we examined the chemical ecology of L. pacifica, the sister species of L. heterotoma. Here, we show that L. pacifica also produces a defensive secretion containing a species-specific mixture of mostly iridoid compounds. However, the composition of the secretion is more complex than in L. heterotoma, and iridomyrmecin is only a minor component. Moreover, in contrast to L. heterotoma, conspecific female competitors were not avoided by female subjects, and a role of the iridoids in the female sex pheromone of L. pacifica can be excluded, as only the females’ cuticular hydrocarbons (CHCs) resulted in the elicitation of courtship by males. Although closely related, the two sister species show substantial differences in the use of the defensive secretion for communicative purposes. Variation in pheromone usage in this genus still presents a conundrum, highlighting the need for additional studies to understand the selective forces shaping the evolution of pheromone composition. Keywords Figitidae · Pheromone · Evolution · Iridomyrmecin · Citral · Cuticular hydrocarbons
Introduction Chemical communication is believed to be the oldest form of communication and is widespread in the animal kingdom (Wyatt 2014). However, the origin and evolution of chemical communication remains a major question in chemical ecology. Several thousand chemical compounds used in chemical communication have been identified Communicated by Marko Rohlfs. The original article has been revised: Due to textual changes. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00049-020-00331-3) contains supplementary material, which is available to authorized users. * Lea C. Böttinger Lea.Boettinger@uni‑bayreuth.de 1
Institute of Evolutionary Animal Ecology, University of Bayreuth, Bayreuth, Germany
(El-Sayed 2020), and the diversity in chemical structures and relative amounts of substances allows an infinite number of complex odor compound combinations. The senderprecursor model posits that pheromone signals can arise via an evolutionary transition from precursor molecules tha
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