Freshwater floodplain habitats buffer native food webs from negative effects of non-native centrarchids and bullfrogs

Species introductions are common in freshwater environments, with the potential to transform community and ecosystem structure. Predatory fishes and American bullfrogs (Rana catesbeiana = Lithobates catesbeianus) are both widespread aquatic invaders implicated in native amphibian declines. In lowland ecosystems, co-occurrence between native and non-native fishes and larval amphibians appears more common than in high-elevation ecosystems, though community interactions there are poorly studied. In this study, we used stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) to examine native fish and amphibian trophic structure in lowland, floodplain waterbodies with and without non-native centrarchid fishes and bullfrogs. In the presence of non-native taxa, three-spine stickleback (Gasterosteus aculeatus), two native salamander larvae, and one of two native frog species shifted their food resources and/or fed lower on the food web, with only one species exhibiting a decline in niche s...