The validity of pairwise models in predicting community dynamics

Pairwise models are commonly used to describe many-species communities. In these models, a focal species receives additive fitness effects from pairwise interactions with other species in the community (\"pairwise additivity assumption\"), and all pairwise interactions are represented by a single canonical equation form (\"universality assumption\"). Here, we analyze the validity of pairwise modeling. We build mechanistic reference models for chemical-mediated interactions in microbial communities, and attempt to derive corresponding pairwise models. Even when one species affects another via a single chemical mediator, different forms of pairwise models are appropriate for consumable versus