Parasite establishment in host communities

Robert D. Holt*, Andrew P. Dobson, Michael Begon, Roger G. Bowers and Eric M. Schauber Department of Zoology, University of Florida, Gainesville, FL 32611, USA Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08540, USA Department of Environmental and Evolutionary Biology, Liverpool L69 3BX, UK Department of Applied Mathematics and Theoretical Physics, University of Liverpool, Liverpool L69 3BX, UK Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL 62901, USA *Correspondence: E-mail: [email protected] Abstract Many pathogens and parasites attack multiple host species, so their ability to invade a host community can depend on host community composition. We present a graphical isocline framework for studying disease establishment in systems with two host species, based on treating host species as resources. The isocline approach provides a natural generalization to multi-host systems of two related concepts in disease ecology – the basic reproductive rate of a parasite, and threshold host density. Qualitative isocline shape characterizes the threshold community configurations that permit parasite establishment. In general, isocline shape reflects the relative forces of interand intraspecific transmission of shared parasites. We discuss the qualitative implications of parasite isocline shape for issues of mounting concern in conservation ecology.