Asymmetries in premating isolating mechanisms in a sympatric species flock of pupfish (Cyprinodon)

We examine cues used in assortative mating in a sympatric species flock of pupfishes (Cyprinodon) from San Salvador Island, The Bahamas. The species are morphologically, genetically, and ecologically distinct. We focus on 2 species, a generalist detritivore and a predator/scale-eater. Experiments show that premating isolation is based primarily on visual cues and is asymmetrical. It is well developed in the less abundant scale-eater but is much less well developed in the more abundant detritivore. Responses of detritivore females from 3 lakes to conspecific and scale-eater males suggest that abundance of the predator also affects development of premating isolating mechanisms in the prey species. These results highlight the importance of frequency-dependent selection and predators in the evolution of premating isolating mechanisms.