Current Research Projects

The evolution of plant-rhizobia interactions
The legume-rhizobium symbiosis is a classic example of mutualism. Leguminous host plants trade carbohydrates for the nitrogen fixed by their rhizobium symbionts. In collaboration with Katy Heath (U. of Illinois), we are investigating how long-term nitrogen deposition treatments at the KBS LTER have influenced the ecology and evolution of rhizobium populations and their Trifolium host plants. Nitrogen-rich environments have been hypothesized to shift the legume-rhizobium mutualism towards parasitism because plants can obtain nitrogen more efficiently from the abiotic environment than from their rhizobium symbionts. We are investigating whether long-term nitrogen addition experiments have caused genetic changes in either rhizobia or host plant populations.

Effects of enemies on exotic vs native plant species.
The Enemy Release Hypothesis (sensu Elton) is one of the key hypotheses explaining the success of invasive species. If invasives commonly escape their enemies and if this enemy release is responsible for their dominance over natives, then excluding enemies may help level the playing field and increase native plant abundance. We established long-term enemy exclosures in swamps, old fields, forests, and restored grasslands to test how enemies influence the relative abundance of native vs. exotic plant species. Many of these exclosures were constructed in public areas and Dave Williams (Lawton High School) is currently developing signage and activities for citizen scientists of all ages to engage in their own data collection on a subset of our plots.

Plant-microbe coadaptation to abiotic stress
In collaboration with Jay Lennon (MSU/KBS, microbiology), I am examining the ecological and evolutionary responses of plants and their associated microbial communities to drought stress. We have completed a multi-generation experiment to investigate both genetic changes in plant populations and changes in microbial community composition in response to drought. The goal of this experiment is to examine whether the presence of a microbial community influences plant ecological and evolutionary responses to drought and whether plants and their belowground microbes show patterns of coadaptation to drought stress.

Global Warming and Biological Invasions
In collaboration with Junmin Li, a visiting researcher from Taizhou University in China, I am studying how global warming influences the growth and reproduction of congeneric pairs of exotic and native species. Although it is hypothesized that global warming will benefit exotic species and harm native species, little empirical data exists addressing this hypothesis. We will use heating rings to simulate global warming in old field environments at Kellogg Biological Station. Similar experiments will be conducted at Junmin's field sites in China, allowing for cross-continental studies of some of our focal species.