My research examines how ecological factors influence evolutionary processes in plants, particularly the origin of new plant species. I examine adaptation and speciation in plants using a range of approaches and tools, including field experiments, molecular techniques, and computer simulations. 

Dissertation: Ecological factors affecting tetraploid speciation in snow buttercups (Ranunculus adoneus: Ranunculaceae)

My doctoral dissertation examined barriers to tetraploid (= 4 sets of chromosomes) speciation in snow buttercups (Ranunculus adoneus) in the Colorado Rockies. I found strong spatial segregation of the diploid (=2 sets) and tetraploid snow buttercups (see figure 1), but no evidence for ecological differentiation.  Strong reproductive exclusion operates to maintain spatial isolation. Stochastic models suggest that limited seed and pollen dispersal can lead to local tetraploid majorities which greatly reduce the barriers to their persistence and establishment.

Postdoctoral Work: Sunflower domestication, crop-wild gene flow, and genome evolution

My postdoctoral work with Dr. Loren Rieseberg at Indiana University and the University of British Columbia focused on barriers to gene flow between crop and wild sunflowers (Helianthus annuus). Populations of wild sunflowers adjacent to the crop retain their distinct morphology despite ongoing hybridization, which suggests that strong selection removes crop alleles. Field experiments in Indiana and Nebraska found that although the traits under selection differed, the loci under selection were the same in the two environments. One allele from the crop was favored at one locus, while an allele from the wild was favored at a second locus.

Research at Luther College

My research at Luther College continues to explore plant adaptation and speciation. I have begun selecting on large seed size in wild sunflowers in an effort to re-domesticate the sunflower from its wild relatives. Early selection likely favored larger seeds, yet the crop differs in many traits besides seed size. Will re-domestication result in the same suite of traits? Work on crop-wild hybrids continues, with the most recent grant focusing on patterns of introgression in long-term hybrid zones.

In addition, I am working with students to examine patterns of drug resistance in E. coli and Staph found in the springs and streams of NE Iowa.

Students work with me as assistants on sunflower research, as part of the team examining drug resistant bacteria, or on their own projects, which have included incidence of Lyme disease in ticks, the effects of endophytic fungi on plant growth, and ploidy variation in Iowa prairie grasses.