CICHLID FISH DIVERSITY THREATENED BY EUTROPHICATION THAT CURBS SEXUALSELECTION

Cichlid fish species of Lake Victoria can interbreed without loss of f ertility but are sexually isolated by mate choice. Mate choice is dete rmined on the basis of coloration, and strong assortative mating can q uickly lead to sexual isolation of color morphs. Dull fish coloration, few color morphs, and low species diversity are found in areas that h ave become turbid as a result of recent eutrophication, By constrainin g color vision, turbidity interferes with mate choice, relaxes sexual selection, and blocks the mechanism of reproductive isolation, In this way, human activities that increase turbidity destroy both the mechan ism of diversification and that which maintains diversity.