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 the
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.