DISSERTATION RESEARCH: Identifying and Measuring Components of Reproductive Isolation Between Terminal Forms of the Ensatina eschscholtzii Ring Species Complex

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The salamander Ensatina eschscholtzii is the most famous example of a 'ring species', a rare situation in which a ring of interbreeding populations surrounds an area of unsuitable habitat and the end populations of the ring exist in the same area without interbreeding. This proposal seeks to identify and measure the barriers to reproduction that prevent gene flow between the terminal forms of Ensatina. Mating trials will be used to test for differences in courtship behavior that may reduce mating between the terminal forms. Parentage will be determined for the offspring of these crosses to investigate patterns of sperm use when females have mated multiple times. Finally, a mark-recapture study will test whether differential habitat preference reduces the opportunity for encountering (and mating with) individuals of the alternative form. This study will provide a detailed case study in nature where barriers that prevent gene flow between incipient species are identified and measured. The project will directly support a graduate student and will include participation by undergraduates from diverse backgrounds. Results will be communicated to the public via the award-winning 'Understanding Evolution' website (http://evolution.berkeley.edu/), a site developed and maintained by UC Berkeley to provide resources for evolution education to teachers and students.