SG: Parasitism as a selective pressure on seasonal migration

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Although monarch butterflies and humpback whales do not look alike, they have one important thing in common: every year, they embark on a seasonal migration that spans thousands of miles. They are not alone. Migration over short and long distances is a widespread animal behavior. Just why so many species risk the perils and uncertainties of migration is a puzzle. Many theories exist to help understand how this seemingly costly behavior evolved. To evaluate these, it is necessary to think small, namely, at the role played by parasites and pathogens. By combining knowledge from animal movement and infectious disease ecology, the researchers will develop mathematical models to study the evolution of migration. This research will not only improve our understanding of host movement and parasites, but will also advance migration theory broadly. Fully understanding what factors drive migration is crucial for predicting how migratory patterns will continue to adaptively change in the future. This project will address a broad range of problems of social and economic interest such as disease spread between migrating wildlife and livestock. It also will help our understanding of the influence of increasing human travel on emergent diseases. The researchers will engage undergraduate students through teaching modules at the University of Minnesota. In addition, they will provide opportunities for independent research projects. The research findings will be communicated to the public at the Bell Museum of Natural History. Despite growing interest in how host migration interacts with infection by pathogens and parasites, there is no rigorous framework to organize, interpret, and predict these interactions. Host movement can either increase or decrease host exposure to parasites and verbal models have generated conflicting predictions. The lack of understanding of when each outcome is likely to occur represents a serious roadblock in our ability to anticipate potential consequences of shifting environmental conditions for both migration and host-parasite dynamics. This research is the first step in overcoming this obstacle. It will use proof-of-concept mathematical models to rigorously test the links between specific assumptions and resulting predictions regarding host movement and parasites. The goal of the work is to develop models that are broadly applicable across systems, but have not yet been considered. Analytical models will be used to test how (a) parasite transmission mode (direct host-to-host-contact versus indirectly through the environment), (b) type of infection cost (survival or fecundity), and (c) spatial/temporal aspects of parasite transmission influence Evolutionarily Stable Strategies. The project will search for the parameter space that promotes evolution of migratory behaviors. The results will highlight certain regions of parameter space as deserving further exploration. This will suggest areas in which more detailed models, parameterized to a specific study system, will be especially useful. The results will also provide a set of theoretical hypotheses that can be tested using already available datasets.