Collaborative research: Disease ecology in the midst of anthropogenic stressors: Exploring the influence of pesticides on host-parasite interactions

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Wild populations are increasingly influenced by human activities including habitat destruction, introduced species, and pollution. As the human population continues to grow, along with our needs for food, our reliance on pesticides to control a variety of pests will intensify. Therefore, pesticides contamination of natural systems will persist. Recent research suggests that some wild populations exposed to pesticides can evolve tolerance over multiple generations or induce tolerance within a single generation. Both of these mechanisms can improve survival when exposed to pesticides. However, each mechanism may lead to different costs that alter the way organisms interact with other members of their community. An increasing number of studies have focused on the effects of pesticides on the interaction between host and their parasites. However, research that examines the influence of evolutionary responses to pesticides on disease dynamics remains limited. The study seeks to understand how evolutionary responses to contaminants may affect host-parasite interactions in aquatic communities. Specifically, the study asks the following questions: (1) Can hosts and parasites evolve tolerance to pesticides? 2) Can hosts and parasites induce tolerance to pesticides within a single generation? 3) How do the two different mechanisms of tolerance influence host-parasite interactions? This research tackles two issues of societal interest such as environmental contamination and transmission of pathogens. In addition, the project focuses on taxa that are declining globally (i.e. amphibians) and habitats that are of increasing conservation concern (i.e. wetlands). The investigators will develop a teaching module for K-12 educators. The teaching module will highlight the role of evolution and ecology in modern toxicology. The study will also provide training for undergraduate and graduate students including minorities, women, and first-generation college students. Overall, this study can provide valuable information that can be used to understand the effects of pesticides from both applied and basic research views.This research will use recent observations of evolved and induced pesticide tolerance in relation to proximity to agriculture as a foundation to explore how pesticide tolerance influences host-parasite interactions. The study will use a parasite (Echinoparyphium) and its intermediate aquatic host species (pond snail and larval wood frog). Using a series of toxicity and host-infection assays across these multiple hosts and parasite life stages, the proposed research will: (1) Analyze landscape patterns of baseline pesticide tolerance across a gradient of agricultural land use. The investigators predict that baseline pesticide tolerance will be higher in parasite and snail populations surrounded by more agriculture than in those surrounded by less agriculture. (2) Evaluate the occurrence of inducible pesticide tolerance in natural populations. The investigators expect a greater magnitude of induced pesticide tolerance in populations surrounded by less agriculture than in those surrounded by more agriculture. (3) Determine the effects of constitutive and inducible pesticide tolerance on host-parasite interactions. The investigators predict that the outcome of the interactions will depend on the relative sensitivity of the hosts and parasites to pesticides.