Evolution of calling songs in the grasshopper subfamily Gomphocerinae (Orthoptera, Acrididae)

The evolution of the calling songs in Gomphocerinae was evaluated via estimating a phylogenetic signal of the song characters and an ancestral character state reconstruction. Analyses of the calling songs in 80 palearctic gomphocerine species allowed us to define 24 characters describing the temporal pattern of the sound and the stridulatory leg-movement pattern. The ancestral song of Gomphocerinae was shown to consist of numerous short echemes lasting on average 0.9 s; each echeme comprised only one syllable produced by movements of only one leg. The next step of the song evolution could be producing longer echemes or longer echeme-sequence. Later, echeme duration again decreased, but this was accompanied by increasing of echeme or syllable complexity. The characters describing the echeme structure were found to be conservative in their evolution. By contrast, most characters of the syllable temporal structure were shown to be relatively labile and more likely under natural or sexual selection. Our study shows that the song evolution in Gomphocerinae implied not only increasing but also decreasing complexity of the syllable temporal structure.