Accuracy of the Lotka-Volterra model fails in strongly coupled microbial consumer-resource systems.

The generalized Lotka-Volterra (GLV) model is a cornerstone of theoretical ecology for modeling the dynamics emerging from species interactions within complex ecological communities. The GLV is also increasingly being used to infer species interactions and predict dynamics from empirical data on microbial communities, in particular. However, despite its widespread use, the accuracy of the GLV's pairwise interaction structure in capturing the unseen dynamics of microbial consumer-resource interactions-arising from resource competition and metabolite exchanges-remains unclear. Here, we rigorously quantify how well the GLV can represent the dynamics of a general mathematical model that encapsulates key consumer-resource processes in microbial communities. We find that the GLV significantly misrepresents the feasibility, stability, and reactivity of microbial communities above a threshold biologically feasible level of consumer-resource coupling, because it omits higher-order nonlinear interactions. We show that the probability of the GLV making inaccurate predictions can be quantified by a simple, empirically accessible measure of timescale separation between consumers and resources. These insights advance our understanding of the temporal dynamics of resource-mediated microbial interactions and provide a method for gauging the GLV's reliability across various empirical and theoretical scenarios.