Building a phylogeny of parasitic wasps in the genus, Cotesia, based on species-specific courtship songs

Background/Question/Methods

Acoustic signals play an important role in premating isolation based on sexual selection within many taxa. Evidence for several genera of parasitic wasps within the Braconidae demonstrates that males produce a characteristic courtship song used by females to identify conspecifics. In Cotesia (Braconidae), courtship songs are generated by wing fanning and repetitive pulses in stereotypical patterns. Our objectives were to determine if male courtship songs within Cotesia are species specific, and therefore could function in premating isolation, and if so, which components differed. We compared songs among 10 of ca. 80 described Cotesia species in North America, including eight species that have not been recorded previously. Songs of emergent males from wild caterpillar hosts in five different families were recorded with miniature omnidirectional microphones in a noise reduction booth. Pattern, frequency, and duration of song elements were analyzed using Raven Pro. Principle component analysis was used to convert the seven elements characterized into three uncorrelated components used in a hierarchical cluster analysis and to group species by similarity of song structure.

Results/Conclusions

Songs among species varied significantly in duration of repeating pulse and buzz elements and in fundamental frequency (175 to 328 Hz). Songs within species were structurally conserved. The first three principle components explained 85% of the variance of song elements. The dendrogram produced by the cluster analysis of principle components generally mirrored the most recent proposed molecular phylogeny for Cotesia spp. by Michel-Salzat & Whitfield (2004), indicating the potential for using courtship songs as a predictor of genetic relatedness. Courtship song analysis may also aid in identifying closely related cryptic species that overlap spatially, and provide insight into the evolution of this highly diverse and agriculturally important taxon.