Linking Host Diversity and Amphibian Disease: Experimental and Field Studies

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Host-parasite interactions are embedded within dynamic, often highly disturbed environments, which can sharply alter patterns of infection and disease risk among hosts. Changes in land use and the resulting shifts in biological communities have been linked to the emergence of pathogens with medical and veterinary importance. However, the ecological mechanisms responsible for increases in infection often remain conjectural. This proposal examines how the ongoing transformation of landscapes surrounding wetlands influences an emerging issue of conservation importance: amphibian limb deformities. The flatworm parasite Ribeiroia ondatrae, which sequentially infects freshwater snails, larval amphibians, and birds, has been linked to widespread limb deformities in amphibians. Infection and the resulting malformations also increase amphibian mortality, potentially causing declines in amphibian populations. Building upon previously funded NSF research and ecological theory, the current proposal combines broad-scale field surveys and mechanistic experiments to understand how land use change, by altering host density and host diversity, will promote or limit Ribeiroia abundance and amphibian malformations. This effort will specifically seek to identify how biodiversity losses in freshwater ecosystems affect the transmission of pathogenic parasites, such as Ribeiroia. Considering the growing number of emerging infections that threaten human health and wildlife conservation, results of the proposed efforts have broad application potential. Ribeiroia is not only growing in conservation importance itself, but is an excellent analog for other parasite infections of economic and human-health significance (e.g., human blood flukes). This proposal would further support cooperative efforts among amphibian biologists and ecologists to address ongoing declines in amphibian populations worldwide.