Research in the lab focuses on both the causes and consequences of behavioral evolution. Using a colorful group of North American freshwater fish called darters, we ask the following questions: Why does mate choice evolve over time? Why has male nuptial color pattern diversified in such spectacular ways in this lineage? How does the rate of behavioral divergence compare with the evolution of other reproductive barriers? Why are individuals attracted only to members of their own species? (For that matter, ARE all individuals necessarily attracted only to members of their own species?) What is the relative contribution of male and female mate preferences to the maintenance of species boundaries?