Parasites represent as many as half of all species of organisms on Earth (1). This rich diversity is driven, in part, by host specificity. Most parasites are host specific, and some parasites are so specific that they only infest only one host species. Intriguingly, however, host specificity is in constant flux. Parasites can, and do, switch to new host species. In fact, one study estimates that as many as 61% of the parasites/pathogens affecting humans have zoonotic origins (2). Furthermore, human introductions of plants and animals into new geographic regions have exposed wildlife to new parasites/pathogens that may ultimately threaten the conservation of global biodiversity (3). My research focuses on the evolutionary ecology of host-parasite interactions. In particular, I am interested in using macroevolutionary information for hosts and their co-evolving parasites to generate testable hypotheses about the evolution of parasite diversity and ecological factors determining host-specificity.
My research involves three major approaches:
- Faunal Surveys - To understand the evolution of parasite diversity and the ecological factors influencing host-specificity we must first understand what parasites exist, where they occur, and which hosts they infest. My research involves faunal surveys of parasites that infest terrestrial vertebrates in China, the Philippines, Nordic countries, as well as local surveys in the Great Basin of the United States. This approach frequently leads to the description of new genera and species, phylogenetic and co-phylogenetic studies of parasites and their hosts, as well as a greater understanding of the relationship between habitat change and parasite diversity, and host-parasite coextinction.
- Comparative Studies - Nature is constantly conducting "experiments". In nature, emergent patterns often unfold over macroevolutionary time, and these time-scales are impossible for a researcher to observe in one life-time. However, investigating the results of these "experiments" in a comparative context allows biologists to beat the clock, and to better understand the evolution of these macroevolutionary patterns. For example, recent comparative analyses conducted in the lab show that feather lice have evolved cryptic coloration to avoid host defense.
- Experimental Work - Faunal surveys and comparative studies document patterns that occur in nature over space and time. These studies frequently generate testable hypotheses about ecological and evolutionary processes. We use Rock Pigeons and their parasites (lice, mites, blood parasites, etc.) as a model system to test these hypotheses. Much of this work involves tests of the efficiency of different adaptations birds have for defending themselves against ectoparasites, ranging from morphological to physiological to behavioral traits, as well as tests of the adaptations that parasites have to avoid host defenses, such as cryptic coloration (camouflage), and escape behaviors (e.g. inserting between feather barbs to avoid preening).
1. Price, P.W. 1980. Evolutionary Biology of Parasites. Princeton University Press, Princeton, NJ.
2. Taylor, L.H., Latham, S.M., and Woolhouse, M.E. 2001. Risk factors for human disease emergence. Philos Trans R Soc Lond B Biol Sci. 356:983-989.
3. Daszak, P., Cunningham, A.A., and Hyatt, A.D. 2000. Emerging Infectious Diseases of Wildlife: Threats to Biodiversity and Human Health. Science 287:443-449.