EVOLUTIONARY SIGNIFICANCE OF INTROGRESSIVE HYBRIDIZATION IN CYPRINID FISHES

BOTANISTS have long recognized introgressive hybridization as important in the evolution of plants1,2. Hybridization among animals is also common3, yet few zoologists have considered it evolutionarily important4-6. We report here that in the genus Gila, a morphologically diverse group of minnows from western North America7, we have discovered a pervasive influence of hybridization throughout their evolutionary histories. Gene exchange among distinctive forms has contributed to existing diversity, supporting the hypothesis that introgressive hybridization can play a significant role in evolution of vertebrates.