One of the most amazing features of the animal kingdom is the diversity of ways in which we communicate. Nearly every animal species is characterized by a unique suite of signals that comprises a specific “language,” from the colorful plumage of the peacock, to the intricate tremulating duets of lacewing insects, to the precise blend of pheromones released by female corn borer moths. A fundamental consequence of this diversity is that individuals of different species typically do not recognize each other as suitable mates and therefore do not interbreed. Differences in mating communication thus form a strong barrier to reproduction between species. Research in my 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 mating communication evolve over time? How does the rate of communication evolution compare with ecological divergence and 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?) Results of past research suggest that in darters, differences in mating behavior may form the first reproductive barrier between diverging evolutionary lineages. My postdoctoral research in the Hawaiian cricket genus Laupala demonstrated that major features of mating behavior (e.g., male courtship song) evolve very rapidly, and that individuals probably use multiple behavioral cues to recognize members of their own species. Our current research focuses on behavioral evolution in darters, in order to determine whether behavioral differences form the primary reproductive barrier between species, and to understand why nuptial coloration has diversified so extensively in this beautiful genus.