The goal of my research is to understand the ecological causes and correlates of plant rarity and invasiveness. I study plants that occur in similar habitats and are closely related. This study includes six species within the genus Cirsium that co-occur in northern California. These species range from federally endangered to noxious invaders.

These Cirsium species differ dramatically in their reproductive success; the endangered species produces the fewest seeds and the invasive species produces the most. I examined whether differences between species in their breeding system and pollination success explain their differences in reproductive success. I quantified pollinator visitation rates and the composition of visiting species, and experimentally measured the magnitude of pollen limitation via a pollen supplementation experiment.

Greenhouse competition experiment. These pots contain the rare plant, Cirsium fontinale, in three treatments: no competition (back plant), intraspecific competition (front left), interspecific competition with Cirsium vulgare (front right).

I conducted a greenhouse experiment to determine the relative competitive ability of these species in different nutrient environments. I hypothesize that the success of the invasive species, Cirsium vulgare may be due to its ability to take advantage of high nutrient environments or persist in low nutrient environments, or in its ability to compete for light and nutrients with surrounding species. Similarly, the low relative abundance of the federally endangered species, Cirsium fontinale, may be due to its lack of competitive ability. I am currently weighing the biomass of these plants, and results from this experiment should be available soon!

My study site at Point Reyes National Seashore.
The rare plant, Cirsium andrewsii, can be seen in this photo.