Despite parasites being found in nearly every community, the relationship between community and disease ecology remains poorly understood. Our goal is to determine the mechanisms by which species interactions and common environmental stressors influence disease properties and community dynamics. Our focal hosts are amphibians, a group of global conservation concern that has been impacted by the recent emergence of infectious diseases. The focal parasites are the trematodes (flatworms) Ribeiroia ondatrae and Echinostoma trivolvis. They are transmitted from snails to amphibians and induce mortality associated with limb deformities and kidney damage, respectively. Our hypothesis is that trematode transmission, associated mortality, and amphibian fitness will depend upon community composition and abiotic stressors. We will conduct surveys to identify relationships among amphibian trematode infections and biotic and abiotic characteristics of wetlands and their surrounding landscape. We will use mesocosm communities to examine how the independent and combined effects of competition and predation (biotic stressors) and pesticides and conditions associated with climate change (abiotic stressors) influence amphibian fitness and disease properties. Additionally, we will elucidate the relationships among amphibian immune responses and biotic and abiotic stressors and infection risk by conducting immunological assays on amphibians from each of our experiments. Finally, we will formulate predictive mathematical models for the spread of trematodes in human-altered environments. This project represents a pioneering effort in the integration of community ecology, immunology, and epidemiology that will improve our ability to forecast future vector-borne disease outbreaks by shedding light on general principles governing host-parasite interactions.
