Genetic, chemical and behavioral investigation of sexual signaling evolution in parasitoid wasps

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One of the most important questions in evolutionary biology is how new species potentially originate. The development and maintenance of barriers to interspecific reproduction has been postulated to be the major driving force of speciation. Generally, two main barrier types can be differentiated according to their function in reproductive isolation either before (prezygotic) or after (postzygotic) formation of an interspecific zygote. In the insect model system Nasonia, a complex of parasitoid jewel wasp species of considerable agricultural importance as selective biological pest control, well-investigated postzygotic reproductive isolation contrasts far less understood prezygotic reproductive isolation. Ubiquitous infections with species-specific Wolbachia bacteria largely prevent hybridizations between the four hitherto described species. However, after antibiotic treatment of the Wolbachia infections, the different Nasonia species regain the ability to hybridize. This not only indicates experimentally accessible and surmountable prezygotic isolation, but also constitutes an extremely useful research tool for studying the genetic architecture of complex adaptive trait differences between the species. My previous studies demonstrated that cuticular hydrocarbons (CHC) in the Nasonia species complex can function as species-specific female sex pheromones distinguishable by the males, hinting at incipient prezygotic isolation. Curiously though, in one species, I discovered an apparently recent evolutionary leap that shifted the female CHC profiles out of the males’ perceptive range, which, in turn, still retain a potentially ancestral attraction to CHC profiles of females from other species. We now have the unique opportunity to track this highly unusual evolutionary shift genetically, phenotypically and behaviourally to unravel the key signaling compounds and obtain a holistic view on the underlying mechanisms. We will combine analytical chemistry, behavioral assays, quantitative genetics and functional genomics to identify the components of the CHC profiles that mediate the female sex pheromone function, determine the genetic basis of the sex pheromonal function and analyze the molecular and evolutionary mechanisms that have led to its differentiation between the four Nasonia species.