Same play, different way: recurrent loss of sexual signals in a field cricket

Evolution has often shown an ability to solve the same problem in seemingly endless creative ways. Here we present an unusually rapid example of this phenomenon, documenting the recurrent loss of sexual signals in populations of Hawaiian crickets (Teleogryllus oceanicus) in real time. Males of this species produce a conspicuous song using specialized wing structures to attract potential mates. However, in Hawaii, this song also attracts a deadly parasitoid fly (Ormia ochracea). In response to this strong natural selection pressure, a new type of male, known as “flatwing,” arose ~20 years ago. These males adaptively lost many sound-producing structures on their wings, leaving them unable to produce songs but ensuring their protection from the eavesdropping parasitoid. More recently, during field sampling, we found males in two different populations that were also unable to produce song, but unlike flatwings, they surprisingly appeared to have intact wing structures.

To understand why these males were unable to sing, we investigated their wing morphology using microscopy, hypothesizing that their loss of song was due to a loss of microstructures that contribute to sound production. We found that in both populations, these males indeed had a highly altered and reduced important microscopic wing structure called the “file.” To determine whether this mechanism differed from that of the silent flatwings that arose two decades ago, we next compared the wings of these new males to old flatwing specimens and found broad morphological differences between the two, confirming that this new male type lost their ability to sing in a novel way. Our findings highlight evolution’s remarkable ability to reach similar outcomes through unique pathways when faced with a common ecological challenge.