My research focuses on understanding the ecological roles of parasites and invasive species in freshwater ecosystems. Current projects are investigating the roles of parasites in food webs, energy flow and nutrient cycling within wetlands; the influence of nutrients on host-parasite relationships; the effects of parasites on host behavior; and the effects of nonnative fish and bullfrogs on native aquatic communities. Much of my work involves the integration of field observations with experiments at various scales. I also make it a priority to extend the impact of my work to society through outreach activities with local students and the public.
These interests form my main areas of research investigations, which are:
- Parasites in Aquatic Ecosystems
- Ecological Stoichiometry and Disease
- Behavioral Ecology and Host-Parasite Interactions
- Invasions in Wetlands
- Tropical Amphibian Declines
Parasites in Aquatic Ecosystems
Although arguably the most common life history strategy on earth, parasitism has historically been omitted from much of food web ecology; One current research focus aims to assess how parasites influence the structure and dynamics of wetland food webs over time. Although arguably the most common life history strategy on earth, parasitism has historically been omitted from much of food web ecology. One current research focus aims to assess how parasites influence the structure and dynamics of wetland food webs over time.
Ecological Stoichiometry and Disease
Ecological stochiometry can link processes within individuals (feeding, assimilation, growth) to processes on the ecosystem scale (nutrient cycling, productivity, food web dynamics). Current research in this area aims to determine how host resource stoichiometry, and mismatches in the elemental composition of hosts and parasites, influences disease. Artificial pond ecosystems (‘mesocosms’) are shown at right in a field at the Hopland Research and Extension Center. Mesocosms are useful for ecological stoichiometry experiments because we can carefully manipulate ratios of nutrients in a controlled manner.
Behavioral Ecology and Host-Parasite Interactions
While parasite-induced mortality and pathology of hosts are often obvious, more subtle effects of parasitism might also have important consequences for ecological communities. We are examining how parasites influence host behavior, both before and after infection. Prior to infection, the “threat” of disease might induce anti-parasite behaviors, similar to the manner in which predators induce certain behavioral changes in prey. This work is being done using trematodes (larval stage shown below) and amphibian larvae.
Invasions in Wetlands
Invasive species have become major drivers of ecosystem change, a problem that is particularly prominent in freshwaters. We have combined regional field surveys with outdoor mesocosm experiments to disentangle the individual and combined effects of two common wetland invaders, the western mosquitofish and the American bullfrog. Ongoing work aims to evaluate how enviornmental variables such as productivity, influence the magnitude of invader impacts on native communities.
Tropical Amphibian Declines
I have recently received funding to begin a project on the eastern slope of the Andes Mountains in Ecuador. The aim of this project will be to disentangle some of the enviornmental drivers of amphibian declines in the area.