Parallel evolution in courtship songs of North American and European green lacewings (Neuroptera: Chrysopidae)




Green lacewings of the Chrysoperla carnea species group use substrate-borne vibrational duetting songs rather than morphology or pheromones for species recognition. Because each of the many cryptic, reproductively isolated song species typically has an extensive geographic range, potentially interfertile biological species are broadly sympatric, and therefore must use distinct regions of acoustic song space if they are to remain reproductively isolated. However, this constraint does not apply to species restricted to different continents, giving rise to the possibility of parallel evolution of song phenotypes between continents. Here we describe a striking example of parallel song evolution, between a known European species, Chrysoperla pallida, and a newly discovered vivid-green North American species, Chrysoperla calocedrii sp. nov. To verify this parallelism, we show that: (1) the songs of the two species have measurably similar multi-volley temporal and frequency structure; (ii) the songs share the same basic genetic pathway; (iii) each species is unable to discriminate between its own and the other's song in playback trials, confirming the acoustic niche overlap; (iv) the two species readily establish normal duets with each other in the lab, leading to copulation and the production of vigorous hybrid progeny bearing an intermediate song phenotype; (v) they have distinct morphologies in both adults and larvae, suggesting different adaptive responses and therefore independent evolutionary histories; and (vi) they occupy relatively distant positions in a Bayesian phylogenetic analysis of 4630 bp of protein-coding mitochondrial DNA, rejecting the alternative hypothesis of similarity through recent common ancestry. We include a formal description of C. calocedrii sp. nov. as a new species, and provide additional observations of its behaviour, ecology, and life history. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 776–796.