Dissertation Research: Selection, niche breadth and plant mating system evolution: Are wider niche breadths of selfing species shaped by water limitation?

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This project will investigate whether the type of plant mating system contributes to whether a plant can survive in stressful habitats. Plant mating systems, which range from self-pollinating to outcross-pollinating, where pollen has to be moved among different plants for fertilization to happen, can have significant effects on where wild plant species live. Self-pollinating species are expected to be better than outcrossing species at colonizing new areas because they do not require the presence of either pollinators or mates. This study will test the hypothesis that self-pollinating species also have physiological advantages that allow them to outperform outcrossing species in stressful, water-limited environments. The researchers will collect and analyze a variety of physiological data, such as growth rate and relative fitness, from multiple, closely-related pairs of selfing and outcrossing Collinsia plants. Results of this work will reveal important factors influencing the evolution of plant mating systems. In addition, the project will involve mentoring of undergraduate students, including individuals from groups that are underrepresented in the sciences. Planned outreach activities include the development of educational activities for elementary school children. Recent findings support theoretical models that suggest selfing may be a niche diversifying trait because it allows colonization of new habitats lacking pollinators or mates. The proposed research builds on previous results on mating systems and niche breadth by testing whether the physiological performance of selfing species relative to outcrossers contribute to the observed repeated patterns of niche breadth differentiation between sister species pairs in the genus Collinsia. To test the hypothesis that selfers are better adapted to water-limited environments, the investigators will measure drought stress by comparing the ratio of stable isotopes 13C:12C in herbarium leaf samples of selfing/outcrossing sister species pairs relative to the 13C:12C in the international standard. They will also grow three selfing/outcrossing sister species pairs in the greenhouse in both high water and water-limited treatments and measure physiological, growth, and reproductive trait responses. Results will have important implications for our understanding of the evolution and maintenance of niche breadth.