Noisy neighbours among the selfish herd: a critical song distance mediates mate recognition within cicada emergences (Hemiptera: Cicadidae)Abstract

Cicadas probably experience mate recognition challenges as a result of the densities that may occur during adult emergence events, and in Okanagana, the most speciose genus of North American cicadas, high alpha diversities during protoperiodical emergences will exacerbate the mate recognition problem. Using 227 songs from 23 taxa, a linear plateau model regressed recognition potential, estimated from linear discriminant analysis, against song distance, revealing a critical song distance of 0.728 standard deviations in z-transformed song parameter space accompanied by a recognition of 91.6%. Based on detailed examination of museum specimen localities, field observations and habitat, taxa were classified as sympatric or allopatric. Sympatric species were separated by song distances that were significantly greater than this critical distance. As expected for mate recognition characters, little within-species variance was observed in the songs of most species, and the relationship between increases in syllable rate and improved recognition was one of diminishing returns. For several taxa that sang with extreme syllable rates of high variance, a mate recognition – sexual selection continuum is proposed. Along this continuum rapid rates simultaneously prevent mate recognition errors while signalling male quality to females.