Collaborative Research: Novel Trophic Interactions Determined by Phytochemistry, Pathogen Infection, and Parasitoids

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In a rapidly changing environment, the value of understanding the complexity of species interactions cannot be overstated. This includes the formation of associations between parasites and novel hosts. This research investigates the interaction between a virus that infects butterflies on both their native food plant, or 'hostplant', and a recently adopted exotic hostplant. This newly discovered virus has unknown consequences for populations of butterflies. However, prior research suggests that the chemistry of the hostplants may have therapeutic effects. How does the outcome of viral infection on individuals and populations of Baltimore checkerspot butterflies depend on the choice of a native or exotic hostplant? The researchers also will study parasitic wasps that attack the caterpillars. Parasitic wasps may alter the entire set of interactions between the butterflies, hostplants and the virus. By understanding disease dynamics within human-altered environments, detrimental impacts on species can be mitigated. This project includes a museum exhibit on the diversity of viruses, a symposium on insect-virus ecology, and the inclusion of undergraduate and graduate student research. All consumers use a subset of the organic resources in their environment. Understanding which resources are used by a particular consumer, and the limitations of those resources, are issues that are both foundational to the ecological sciences and important for understanding rapid global environmental change. Herbivorous insects are central to general theory to understand dietary niche breadth. The relevant resources (hostplants) are discrete and experimentally tractable, and herbivorous insects are key to terrestrial ecosystem function. A relatively understudied element of dietary breadth is the process of host expansion, when new hostplants are adopted into the diet of an insect herbivore. This project takes advantage of a recently formed interaction between the Baltimore checkerspot butterfly (Euphydryas phaeton, Nymphalidae) and the exotic narrow-leaved plantain (Plantago lanceolata, Plantaginaceae) to develop mathematical models for macroparasite population dynamics on a novel plant species. Predictions will be tested using laboratory and mesocosm experiments that include infection with butterfly 'enemies', a naturally-occurring pathogenic virus and parasitoid wasp, both of which attack caterpillars of the butterfly. The overarching question of this project is: Can we predict persistence of the butterfly populations from the interactions with enemies on native and exotic hostplants? While addressing this larger question, the study will improve our empirical understanding of virus and parasite ecology by investigating dose dependent effects of the pathogen, virus transmission, and caterpillar survival mediated by hostplant chemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.