ASYMMETRIC MATING PREFERENCES ACCOMMODATED THE RAPID EVOLUTIONARY LOSS OF A SEXUAL SIGNAL

Rapid evolution has been well documented in naturally selected traits, but few examples exist for sexually selected traits, particularly sexual signals. This may in part be due to the complex set of behaviors associated with sexual signals. For a sexual signal to change, the change must be favorable for the signaler, but must also be accommodated by the receiver's perception and preferences. We investigated female accommodation of an extreme change in the sexual signal of Polynesian field crickets, Teleogryllus oceanicus. The cricket is native to Australia, widely distributed on Pacific Islands, and was recently introduced to Hawaii. Selective pressure by a deadly parasitoid fly favored a wing mutation in Hawaii (flatwing) that eliminates males' singing ability altogether. Despite conventional wisdom that females require males to produce a courtship song before mating, we show that females from ancestral, unparasitized Australian and Pacific Island populations as well as parasitized Hawaiian populations, will mate with silent flatwing males, suggesting this behavioral option predates the change in sexual signal. Furthermore, ancestral Australian females discriminate against flatwing males more severely than island females. We suggest island colonization favored females with relaxed mating requirements (Kaneshiro's effect) facilitating the rapid evolutionary loss of song in Hawaii.