Ecological Speciation and the Physiological Performance of Plant Hybrids in Ipomopsis

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The proposed research addresses ecological mechanisms by which new species are formed and maintained. In plants, one mechanism involves natural selection mediated by pollinators: two flower species specialize on different animal pollinators, and hybrids receive low pollination. Another possibility is environment-mediated selection: differences in selection between habitats produce genetic incompatibility in hybrids or poor physiological adaptation of hybrids to parental environments. Environment-mediated selection will be tested by measuring physiological performance and fitness of Ipomopsis hybrids and parental species. First, physiological traits (including photosynthesis, water-use efficiency) will be measured as functions of environmental variables. Second, seeds of varying genetic background will be planted into different habitats and followed to test whether divergent vegetative and physiological traits are favored in the two parental habitats. The strength of environment-mediated selection will be compared with pollinator-mediated selection. DNA samples will be stored for future genetic mapping of critical traits. This work integrates physiological methods into the study of evolutionary processes. It will help explain why plant hybrids vary in fitness and contribute to knowledge of speciation, a fundamental issue in evolution. The results have potential benefits to agriculture and conservation. They may help in predicting conditions influencing escape of genes from genetically modified crops into wild relatives, and hybridization between invasive and native plants. The research provides training for undergraduate, graduate, and postdoctoral students.