A major unsolved question in biology is why plant populations often maintain a mixture of two reproductive strategies, self-fertilization and cross-pollination. Long standing genetic theories predict that these should rarely co-exist. Yet this dual strategy is surprisingly common in nature, suggesting that existing theory is inadequate. This project tests the hypothesis that ecological interactions among plant species help maintain dual strategies. When multiple plant species flower together and share pollinators, pollen is often wasted on flowers of other species, reducing the benefits of cross-pollination. The researchers will evaluate this hypothesis through a combination of theory development, field studies of pollinator behavior, and molecular genetic studies of parentage. This research will enhance conservation of plant and pollinator communities and will help scientists understand how invasive species and habitat fragmentation influence pollination. A partnership with an economically-disadvantaged K-12 school will foster improved understanding of conservation and biodiversity.
Focusing on the perennial plant Mimulus ringens, empirical and theoretical studies will investigate how pollinator sharing affects the tradeoff between outcross siring and selfing. Manipulative experiments will evaluate whether changes in the ecological context, the abundance of a co-flowering species Lobelia siphilitica, influence patterns of natural selection on selfing. Comparisons of 32 natural populations that vary in the type and abundance of co-flowering species will provide information on selfing rates, pollen limitation, floral morphology, and inbreeding depression, and evolutionary responses. Models will be developed using an adaptive dynamics approach that will incorporate the automatic advantage of selfing, evolutionary changes in inbreeding depression; it will account for pollen loss caused by the presence of a co-flowering species, and will explore the range of genetic and ecological factors that could generate stabilizing selection on mixed mating. These linked empirical and theoretical investigations will provide a broad new framework for understanding the evolution of plant mating systems.