Background: Behavioral isolation is the reduction in interbreeding between species due to differences in mating signals and preferences. Behavioral isolation is thought to evolve rapidly among species with strong sexual selection. Male darters appear to experience strong sexual selection for nuptial coloration.
Question: Does behavioral isolation evolve faster than other reproductive barriers to gene flow? Is behavioral isolation best explained by differences in male nuptial color and/or the environment?
Methods: Multiple pairs of species are examined for multiple reproductive barriers to determine whether behavioral isolation evolves first. Indices developed to quantify environmental and male color differences between species are compared to the strength of behavioral isolation.