Energetic feasibility in ecological systems

Abstract

Ecological systems persist by routing resource and energy fluxes through interacting components. Yet external supply alone does not determine whether a community can be sustained: resources must be captured, redistributed, and processed at rates that are jointly compatible across the system. Here we connect ecological energetics, consumer-resource theory, network ecology, and feasibility theory to ask which environmental conditions can energetically support a given ecological organization. This synthesis provides a common geometric representation in which saturating resource capture and internal flux routing translate component-level energetic constraints into a multispecies feasibility domain. Using microbial cross-feeding as a worked example, we show how ecological organization shapes this domain and how the fraction of feasible configurations changes with total input. Increasing input initially expands feasibility by relieving energetic limitation, whereas further input can reduce it when routed flux exceeds productive throughput and cannot be fully accommodated through storage, export, dissipation, or redistribution. This shift in the dominant constraint can generate an intermediate-input window in which energetic feasibility is maximized. A reanalysis of a longitudinal human gut microbiome reveals a corresponding empirical signature: recurrent microbial assemblages most frequently reach their highest occurrence frequencies at intermediate caloric intake across community sizes. By connecting concepts and theories that are often treated separately, this synthesis shows that energetic feasibility is a systems-level property arising from the interplay between environmental supply, internal flux routing, and ecological organization.