Roaming Romeos: male crickets evolving in silence show increased locomotor behaviours

Loss of sexual signals should be strongly selected against when these signals are necessary for mate attraction or acquisition. Male Teleogryllus oceanicus field crickets produce a long-distance calling song to attract females. Separate genetic mutations recently evolved on the Hawaiian Islands of Kauai and Oahu, rendering approximately 90% and 50% of males, respectively, incapable of calling. We examined whether males from three populations, each with a distinct prevalence of this silent ‘flatwing’ phenotype, show behavioural plasticity in response to being reared in a call-less environment. Crickets from Kauai, Oahu and Mangaia, a Cook Islands population without the flatwing phenotype, either were or were not exposed to calling song during late juvenile and early adult development. Movement assays showed that when males originating from Kauai were reared in silence, they moved sooner, moved more and spent more time walking during silent behaviour trials than did their counterparts reared with calling song. Males from Oahu and Mangaia, however, showed no such effect of acoustic rearing environment on these behaviours. This suggests that there has been directional selection on Kauai for males to respond to a silent environment by increasing their mobility, thus compensating for their lack of song and increasing their chance of encountering receptive females. •Some male crickets have lost the ability to sing, making it hard to attract mates.•Males from a population with >90% silent males move more when reared without song.•Treatment did not affect crickets from populations with few or no silent males.•Males that increase movement can increase their chances of finding mates.•Plasticity in this behaviour may be under selection when calling males are rare.