Dissertation Research: Ecological Causes of the Evolution of Self-Pollination in Clarkia xantiana: The Role of Geographic Variation in Biotic Interactions

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The proposed work tests hypotheses on the causes of the evolution of self-pollination in Clarkia xantiana, a native annual plant composed of an outcrossing and a self-pollinating subspecies. Previous work shows that the two subspecies differ in geographic range, plant community associations, and population size. This project examines the role of plant population size and plant community interactions in determining the abundance of pollinating bees and whether an outcrossing versus self-pollinating mating system is advantageous. The proposed work investigates (1) the distribution and abundance of specialist bee pollinators with respect to the mating system and population attributes of C. xantiana, (2) the factors affecting whether reproductive output is limited by the abundance of pollinators, and (3) the effects of population size and the plant community on the relative success of C. xantiana individuals that vary in mating system. A combination of field observations, field experiments, and molecular genetic analyses will be employed to address these problems.The evolution of self-pollination is among the most common events in the evolutionary history of flowering plants. While the biological consequences of self-pollination (e.g. inbreeding) are well known, the ecological causes of this evolutionary transition have rarely been considered. This project will also provide new information on the importance of native bee communities and plant communities in the viability of plant populations.