Because closely related species often differ in habitat, ecological differences could be important in speciation. The two possible mechanisms of ecological speciation are called extrinsic and intrinsic isolation. Extrinsic isolation occurs when hybrids that are intermediate in form cannot find appropriate habitat. Intrinsic isolation occurs when hybrids have reduced fitness regardless of habitat, that is, the problem has to do with internal factors such as hybrid physiology. The challenge is to determine which kind of isolation arose first and their relative contributions to allowing populations to continue towards being distinct species. For most animals, speciation takes too long to observe directly, but some can be caught in the process of speciation. Such species are ideal for making inferences about the order and magnitude of extrinsic and intrinsic isolation because populations can be studied at various stages of divergence, from recently diverged to completely unable to hybridize. This project focuses on ecological speciation among populations of killifish, which are ideal for studying ecological speciation because populations have diverged across a gradient from freshwater to saltwater multiple times. The PI will measure extrinsic and intrinsic isolation between freshwater and saltwater populations and compare the results with those from populations that are found in similar salinities.

Teachers and biology education majors are incorporated into nearly all the proposed activities; they will conduct research and develop curriculum materials. The goal of the PI is to provide a thorough understanding of speciation through participation in research. A yearly seminar event will be held on teaching evolution to create an ongoing discussion between educators and scientists. Finally, a summer workshop will be held to educate local teachers about evolution and disseminate the curriculum materials developed through this project.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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George W. Gilchrist
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University of Illinois Urbana-Champaign
United States
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