Female responsiveness underlies the evolution of geographic variation in male courtship between allopatric populations of the fish Girardinichthys multiradiatus

Traditionally, the origin of new species from disjoint populations has been thought to be due to the accumulation of mutations, genetic drift, or to local, divergent adaptation. It has also been proposed that sexual selection can accelerate, or even generate, reproductive isolation. Although there is some evidence that female choice is strong enough to generate reproductive isolation, the mechanism by which isolation is produced is still poorly understood. Here we show that (1) the population-characteristic male courtship behaviour of the amarillo fish (Girardinichthys multiradiatus, Meek) is modified in the presence of females from other populations, that (2) this is due to the males responding to subtle cues from females, but that (3) the resulting courtship style does not match the female's population-characteristic behaviour. We conclude that the interplay between male courtship and female responsiveness has led to the evolution of local variants in courtship style that hamper communication between allopatric individuals and promote pre-mating isolation.