Broadly I am interested in using invasive plants as natural experiments to test how evolution can occur in natural habitats. Invasive species can be a powerful tool because we can often trace specific events to their genetic consequences and because novel selection pressures often prompt rapid evolution. My graduate research has centered around invasive Japanese knotweed.
Population genetics of Japanese knotweed in North America
Japanese knotweed has a complex populations structure because it reproduces asexually, but hybridizes with a similar species, Giant knotweed. To complicate matters, Japanese knotweed is octoploid, but Giant is tetraploid. Using Genotyping-by-Sequencing, we were able to show that North American populations contain just one genotype of Japanese knotweed, but several Giant knotweed genotypes and at least two hybrid zones.
Knotweed occupies a large niche, so we would expect to find local adaptation in disparate populations. However, reciprocal transplantation of individuals showed that individuals in the northern part of the range were equally fit in southern habitats and vice versa. Populations retain some trace of their home habitat, however, suggesting genetic or epigenetic differentiation.
In the Adirondack mountains in New York, land managers have consistently sprayed populations of knotweed with glyphosate herbicide. We showed that stands within the park were not biochemically resistant to the herbicide, but were better able to re-grow following treatment than stands that had never been sprayed.