DISSERTATION RESEARCH: Theories of Adaptive Radiations: A Test Using the Family Percidae (Teleostei: Perciformes)

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Dr. Richard L. Mayden and Mr. Nicholas J. Lang of Saint Louis University will study the evolution and ecology of the family Percidae; a Holarctic group of freshwater fishes. The family is comprised of 10 genera and over 200 species distributed across North America and Eurasia. The North American endemic tribe Etheostomatini (4 genera and nearly 200 species) represents the vast majority of species-level diversity within the family. This group of fishes exhibits many characteristics of the classic adaptive radiations (African rift lake cichlids, Galapagos finches) including high diversity, strong sexual dimorphism, and a range of ecological specializations. Recent theoretical advances have allowed for the objective identification and characterization of adaptive radiations. In order to implement these tests within the percids, the awardees will construct a hypothesis of evolutionary relationships within the family using nuclear and mitochondrial DNA sequences, as well as morphological and behavioral characters. These relationships will be used to identify and test hypotheses about the processes through which adaptive radiations form. This project will train a doctoral student. In addition, adaptive radiations are, quite literally, the foundation for modern ideas about evolutionary biology. Recently devised methods have allowed biologists to focus on those groups of organisms that display a wide range of adaptations regardless of how many species are included. This has focused research on groups that have evolved into new niches instead of those that have many species within a retained ancestral niche. Darters (the common name for Etheostomatine fishes) are a diverse group that inhabits many niches in all possible types of freshwater bodies in North America. There are several lineages of darters, each of which inhabits a characteristic microhabitat. While representatives of divergent lineages often segregate by microhabitat within a local fauna, it is rare for closely related species to inhabit the same stream. The hypothesis that diversification into new niches drove early darter evolution, while vicariance and/or local sexual selection are the factors underlying high levels of species diversity, will be tested using a comprehensive phylogenetic tree. This tree will be useful to many future scientists interested in both evolutionary and ecological processes within this interesting group.