Sexual signals may be acquired or lost over evolutionary time, and are tempered in their exaggeration by natural selection. In the Pacific field cricket, Teleogryllus oceanicus, a mutation (“flatwing”) causing loss of the sexual signal, the song, spread in <20 generations in two of three Hawaiian islands where the crickets have been introduced. Flatwing (as well as some normal-wing) males behave as satellites, moving towards and settling near calling males to intercept phonotactic females. From 2005 to 2012, we surveyed crickets and their responses to conspecific song, noting the morph and number of males and females before and after experimental playbacks. The three Hawaiian islands consistently contained different proportions of flatwing crickets, ranging from about 90% of males on Kauai to 50% on Oahu to rare on the Big Island of Hawaii. Flatwing and normal-wing males do not appear to differ in responsiveness to playback, a behaviour that should influence the likelihood of a male encountering a phonotactic female. Instead, male and female crickets from populations in which little to no calling song is perceptible during development tended to seek out callers more readily than crickets that developed in noisier environments. Such increased phonotaxis makes females more likely to find either the caller to which they are responding or to encounter a flatwing (or normal male satellite) that has also been attracted to the song. Our evidence suggests that pre-existing behavioural plasticity (manifest as flexible responses to social—particularly acoustic—information in the environment) is associated with the rapid spread of the flatwing trait. Different social environments select for differential success of flatwing or normal-wing males, which in turn alters the social environment itself.
Bibliographical noteFunding Information:
We are grateful to the many people who have participated in the surveys over the years, most notably Robin Tinghitella, Elizabeth Swanger and Susan Balenger. We thank the Kauai Agricultural Research Station, the University of Hawaii, Brigham Young University in La’ie, and many tolerant community members in various neighbourhoods throughout Hawaii for allowing us to sample crickets. The staff of the Dolphin Bay Hotel in Hilo has been remarkably helpful and supportive, and we particularly thank John Alexander for the numerous “cricket discount rates” we have received over the years. N.W.B. received funding from Natural Environment Research Council fellowships (NE/G014906/1 and NE/L011255/1). M.Z. is supported by grants from the US National Science Foundation and by the University of Minnesota. The authors declare no conflict of interest.
© 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society
- Teleogryllus oceanicus
- behavioural preadaptation
- field cricket
- natural selection
- phenotypic plasticity
- rapid evolution
- sexual selection