The Evolution of Plant Mating Systems.

Evolution of self-compatibility in Leptosiphon.  We are interested in the ecological and genetic factors that play a role in the evolution of self-fertilization from self-incompatibility – a genetic mechanism that allows a plant to recognize and reject its own pollen to promote cross-fertilization.  Our research has focused on Leptosiphon, a genus of California annuals that exhibits remarkable variation in breeding system traits.  Leptosiphon jepsonii has an unusual and variable breeding system that provides us with a unique opportunity to study the breakdown of self-incompatibility.  The flowers of most L. jepsonii plants are initially self-incompatible, becoming capable of selfing later in anthesis; other plants are self-compatible when flowers first open.  The frequency of these different phenotypes ranges widely among populations, allowing us to explore how outcrossing rate, inbreeding depression, reproductive assurance and other parameters are correlated with variation in self-compatibility.  Interestingly, our crossing and selection studies show that different genes control the timing of self-compatibility in different populations, suggesting that there are multiple genetic pathways to the breakdown of self-incompatibility.  This project has been funded by NSF and has yielded two Master's theses.

Hybridization and Plant Breeding Systems. Our work has also focused on the complex interactions between breeding systems and hybridization and their evolutionary consequences.  Self-incompatible plants appear to have a greater ability to screen out foreign pollen than self-compatible species.  On the other hand, self-fertilization can strengthen reproductive isolation between species. We are investigating these and other factors in a study of two species of Leptosiphon that co-occur in California.

Cleistogamy in Triodanis.  In recent work, I have begun to develop two species in the genus Triodanis (Venus’ looking glass) as a study system for evolutionary questions on cleistogamy. Cleistogamy refers to the production of modified flowers that do not open and therefore produce seeds solely by self-fertilization.  Triodanis is a genus of widespread weedy annual species. Two species of Triodanis in North Carolina (T. perfoliata and T. biflora) present opportunities for investigations into this phenomenon and its evolutionary implications.

Long-term Ecological Studies of a Wetland Plant Community. 

	Experiment history and design. We are studying the long-term effects of nutrient addition and disturbance on a plant community at a site near the ECU campus.  In seven years of study, we have observed significant decreases in diversity in fertilized and unmowed plots, and changes in the relative abundance of forbs, grasses and woody species. Initiated with NSF funding, this project involves undergraduate biology students in authentic ecological research at realistic spatial and temporal scales.  The project has also yielded a Masters thesis.
	Evolution in ecological time. With new funding from NSF, we are developing tools to test for adaptive evolution and changes in population genetic structure in response to the experimental treatments.  We are generating AFLP genetic markers and developing greenhouse cultivation methods for 4-5 target plant species that are present throughout the long-term ecology plots, including Euthamia caroliniana (slender goldentop) and Packera tomentosus (woolly ragwort).  Soil microbial community.  In collaboration with Dr. Matt Schrenk (ECU) we are extending the project to explore the effects of treatments on the soil microbial community.  Fertilizer and mowing treatments might affect soil communities either directly, or indirectly through differences in plant community composition.  In turn, changes in soil microbes community might affect plant growth.  Using an environmental PCR approach to identify microbial species present, we have found preliminary evidence for dramatic differences in community diversity and composition in fertilized vs. unfertilized plots.