Collaborative proposal: Latitudinal variation in top-down and bottom-up control of salt marsh herbivores

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Description. Interest in latitudinal patterns of biodiversity and species interactions is centuries old. Studies of latitudinal variation in individual interactions suggest that plant defenses, herbivory and predation are all more intense at lower latitudes. However, because these processes interact and are spatially correlated, understanding latitudinal patterns of biodiversity and food-web structure will require a more sophisticated experimental approach than exists to date. Atlantic coastal salt marshes are ideal systems for examining interactions between multiple trophic processes that vary across latitude. Three major food-web factors change in parallel in salt marsh plant systems across latitude: plant quality, habitat structure, and the presence of top predators. The PIs will experimentally examine how spatial variation in these factors leads to different controls on herbivore abundance and food web structure across latitude. Significance. Ecologists have a long-standing interest in geographic patterns, but this project will be the first to experimentally investigate spatial variation in top-down and bottom-up forces across a latitudinal gradient. The results will increase our understanding of food-web structure, omnivory, spatial variation in interactions, and general salt marsh ecology. The project will use utilize existing networks of research reserves (NERR, LTER) train a postdoc, two graduate students and two undergraduates, and include outreach to K-12 educators.