Hyperdiverse songs, duetting, and the roles of intra- and intersexual selection in the acoustic communication of the genus Eurycorypha (Orthoptera: Tettigonioidea, Phaneropterinae)

Abstract

Acoustic communication is an essential part of the mate-finding system of many insects, e.g., ensiferan Orthoptera. In this group, the signals consist typically of relatively simple repetitive sound patterns produced for long times and used by the females for a phonotactic approach to the singing males. However, the situation can be different in duetting species where the females respond acoustically to the male. Here, we present data of the songs of 14 East African species of the duetting genus Eurycorypha. These songs are extremely diverse differing in many parameters and containing up to three different syllable types grouped into various echemes. In the duets between males and females, studied in 7 species, the females respond with latency times between 100 and 400 ms and are in some species able to react to different trigger syllables or also to the end of a series of syllables. The males often modify their songs after having heard a female response. Some of these modifications are also produced spontaneously. Similar elements are even found as integral part of the calling song in some species. We interpret these modifications aimed to protect a duet against eavesdropping rivals and thus as part of intrasexual selection. The evolution of the complicated song patterns may thus be driven by the interaction between female choice s.l. and male-male competition.