Cuticular hydrocarbon divergence in the jewel wasp <i>Nasonia</i>:Evolutionary shifts in chemical communication channels?

The evolution and maintenance of intraspecific communication channels constitute a key feature of chemical signalling and sexual communication. However, how divergent chemical communication channels evolve while maintaining their integrity for both sender and receiver is poorly understood. In this study, we compare male and female cuticular hydrocarbon (CHC) profiles in the jewel wasp genus Nasonia, analyse their chemical divergence and investigate their role as species-specific sexual signalling cues. Males and females of all four Nasonia species showed unique, nonoverlapping CHC profiles unambiguously separating them. Surprisingly, male and female phylogenies based on the chemical distances between their CHC profiles differed dramatically, where only male CHC divergence parallels the molecular phylogeny of Nasonia. In particular, N.giraulti female CHC profiles were the most divergent from all other species and very different from its most closely related sibling species N.oneida. Furthermore, although our behavioural assays indicate that female CHC profiles can generally be perceived as sexual cues attracting males in Nasonia, this function has apparently been lost in the highly divergent female N.giraulti CHC profiles. Curiously, N.giraulti males are still attracted to heterospecific, but not to conspecific female CHC profiles. We suggest that this striking discrepancy has been caused by an extensive evolutionary shift in female N.giraulti CHC profiles, which are no longer used as conspecific recognition cues. Our study constitutes the first report of an apparent abandonment of a sexual recognition cue that the receiver did not adapt to.