DISSERTATION RESEARCH: The interaction of environmental context and host attributes in driving parasitism

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At a time when ecosystems are rapidly transforming, it is important to clarify how environmental change affects disease risk for animals. Understanding the impact of warming on disease has gained special urgency due to climate change, but its net effect remains controversial and elusive. This study will explore how water temperature alters aquatic host-parasite interactions by testing whether shifts in growth and development could mismatch the life-cycles of a host and its parasite, a mechanism that is believed to be important in the climate change context, although direct tests of it are uncommon. This study constitutes a further step toward identifying which outcomes for disease are likely to dominate as the climate changes and will contribute to a framework for predicting effects of temperature on host-parasite interactions. The broader impacts of this work include 1) teaching K-12 students and the public about host-parasite interactions, 2) mentoring undergraduates, including under-represented groups, to do independent research and engage the public through outreach, and 3) developing the plot of an interactive children's book about the mayfly-parasite relationship. All of these efforts focus on small animals (e.g., parasites and invertebrates) to increase awareness of the full scope of biodiversity.After measuring a suite of environmental variables in mountain streams (Colorado, USA), evidence suggests that warmer temperatures decrease the prevalence of nematode worms infecting mayflies. That observation, combined with previous findings that warmer temperatures accelerate the developmental rate of mayfly hosts, suggests that the mismatched timing of host and parasite life-cycles could decrease parasitism in warmer areas. Because temperature cannot be readily disentangled from other environmental variables in nature, a controlled microcosm experiment will be used to test the hypothesis that warmer water causes faster development of mayflies, thereby decreasing the overlap of susceptible (early instar) hosts with infective parasites, and ultimately reducing parasite infections.