Food Web Similarity Increases With Productivity Similarity at a Continental Scale

Primary productivity and trophic interactions are fundamentally linked. However, it remains largely unknown how food web structure varies along primary productivity gradients at continental scales or how the influence of primary productivity on food webs varies within regions. Furthermore, anthropogenic pressure threatens the integrity of food webs globally with potentially predictable food web disassembly. Here, we test how plant productivity and anthropogenic fragmentation predict the pairwise similarity of food web networks within and among regions for 127 protected areas spanning deserts to rainforests. We measured food web structural equivalence independent of species identities and accounted for inherent scaling of food web structure with richness and connectance. Food webs were significantly more similar at sites with similar plant productivity at the continental scale and within woodland savannas, and in tropical rainforests with similar anthropogenic fragmentation. These empirical results inform how food web structure mediates biodiversity and ecosystem function.