Several hypotheses could explain the evolution of multimodal signals. One possibility is that such signals allow for communication even when one signalling modality is temporarily unavailable. However, little is known about the consequences of the permanent evolutionary loss of a signal modality. We used the field cricket Teleogryllus oceanicus to test the hypothesis that the loss of one mode of signalling can be accommodated by flexibly switching to another pre-existing modality. Field crickets use cues that carry social information in the form of both long-range acoustic signals and short-range cuticular hydrocarbons (CHCs), but males in some T.oceanicus populations have permanently lost the ability to sing because of a morphological mutation erasing sound-producing structures on their wings. In assays testing responsiveness to substrate-borne CHCs, T.oceanicus females responded to the presence of male, but not female, CHCs, which is consistent with known sexual dimorphism in field cricket chemical cues. However, we found no evidence for signal compensation in male crickets that have experienced an evolutionary loss of acoustic signals: females did not differentially respond to the CHCs of constitutively silent males compared to those of normal males. The ability of organisms to shift adaptively from one signalling modality to another following the evolutionary loss of a signal is likely to be constrained by both the degree to which signal production and receiving is flexible and the existence of suitably preadapted alternative modalities.
Bibliographical noteFunding Information:
We thank J. Wang and A. Leung for help maintaining crickets and for assistance carrying out behavioural trials. We also thank J.T. Rotenberry for helpful feedback, as well as R. Rutowski and two anonymous referees for comments that greatly improved the manuscript. B.G. was funded by a National Science Foundation (NSF) Graduate Research Fellowship and a University of California Riverside Graduate Research Mentorship Program Fellowship, M.Z. was funded by the National Science Foundation ( 1122244 ), and N.W.B. was funded by the Natural Environment Research Council ( NE/G014906/1 ).
- Chemical cue
- Cuticular hydrocarbon
- Field cricket
- Multimodal signal
- Teleogryllus oceanicus