The document summarizes an experiment on mate selection in two closely related cichlid fish species, Pundamilia pundamilia and P. nyererei. The experiment tested the hypothesis that female cichlids choose mates based on male coloration. Results showed that under normal light, females preferred males of their own species, but this preference disappeared under orange monochromatic light. This suggests that variation in light conditions in their native habitat impacts whether the species interbreed or remain distinct, representing a form of diversifying selection through sexual selection.