Predator Diversity Changes the World: From Gene to Ecosystem

Abstract

Trophic polymorphism, defined as the state in which two or more clearly different feeding functional traits exist within the same population of a species, is general in fishes. In aquatic ecosystems, the fishes often have strong impacts on prey communities as keystone predators, so that phenotypic divergence of their feeding traits can alter biotic and abiotic attributes of environments through changes in the form of trophic interactions. The predator-induced environmental alterations may, in turn, drive evolutionary changes in adaptive traits of themselves as well as of other members in the communities. This process, in which ecology and evolution reciprocally interplay over contemporary time-scales, is termed "eco-evolutionary feedback." In this chapter, we review how and when trophic polymorphism has been generated in fish populations and then discuss what consequences it has in ecological and evolutionary aspect. Special references are made to the case in the ancient Lake Biwa, which has a geological history long enough for divergent fish populations to come to ecological speciation and thus provides a good opportunity to understand how such an evolutionary process diversifies biological communities and consequently ecosystem properties in lakes.