Adaptive radiation and the role of ecology in neotropical cichlid fish divergence

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Rivers of South and Central America harbor more than 6000 species of freshwater fishes, the most diverse fish fauna on Earth. Remarkably, little is known about the origin of this astonishing diversity. Research funded by this proposal will study the evolution of Neotropical fishes using the family Cichlidae as a model. Our previous and ongoing work indicates that at least one group of American cichlids, the Geophaginae, diversified through a process known as adaptive radiation. This rapid diversification was probably associated with invasion of previously unoccupied ecological niches by lineages that would become the modern genera of Neotropical geophagines. Based on these results, we hypothesize that other groups of South and Central American cichlids may have also diversified by adaptive radiation. We will test this hypothesis by describing the evolutionary history of all Neotropical cichlids, reconstructing past events in their evolution and uncovering the forces that drove their diversification. Additionally, we will assess the importance of ecological pressures in Neotropical cichlid speciation by studying the modern ecology and genetics of the cichlid genus Geophagus from South America. Understanding how the diversity of South and Central American cichlids originated will shed light on the processes responsible for the origin of tropical freshwater fish in particular and biodiversity in general. This study should pave the way for future efforts to understand Neotropical freshwater fish evolution. The project also will generate extensive data on the ecology of Neotropical cichlids. This information should help conservation efforts and reveal potential vulnerabilities of tropical fishes and their environment to mounting threats in the form of unregulated fisheries, habitat modification for agriculture and hydroelectric development, and increasing demand on water resources.