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. Genome-wide screening of microsatellite frequencies between the crop and adjacent wild populations has identified one locus with an unknown function that has a very large genetic distance, suggesting that strong selection is at work.

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 selection on crop-wild hybrids continues, with field plots in Iowa and North Dakota.

Collaboration with the University of Queensland in Australia

In collaboration with Dr. Daniel Ortiz-Barrientos at the University of Queensland in Australia, I will be examining ecological processes that maintain species barriers between the common sunflower, Helianthus annuus, and the prairie sunflower, Helianthus petiolaris. We previously crossed the two species to make F1 plants, and then back-crossed them to the parental species. Lineages that should have been genetically similar unexpectedly had differences in survival and fitness when grown in the field.  We will investigate how the mitochondria is shaping fitness, possibly through the imprinting of genes.

Projects Focused on Plants in Northeast Iowa

Finally, I have initiated several projects focusing on plants in northeast Iowa. First, what evolutionary changes will occur in response to allelopathic invaders? Garlic mustard and spotted knapweed produce compounds which inhibit soil fungi and neighboring plants in North America, but do not have the same effect in Europe. Can native plants and fungi adapt to these invaders?

A second project is investigating levels of chromosome number variation in Iowa prairie grasses and forbs. Many of these plants are known to vary across their range, but so far detailed studies of their distribution in NE Iowa have never been carried out.

Northeast Iowa has many species that are at the edges of their distribution, especially on our cool, north facing limestone slopes. How will these plants respond to climate change? Will the primary challenge be physiological stress due to increased summer temperature, or will new competitors, herbivores, and diseases be more important? To address this, I have begun studying plants on these slopes in the hopes of identifying the key pressures that might limit their persistence in Iowa.