Integrating metabolic scaling and coexistence theories

Abstract

Metabolic scaling theory has been pivotal in formalizing the expected energyexpenditures across populations as a function of body size. Coexistence theoryhas provided a mathematization of the environmental conditions compatiblewith multispecies coexistence. Yet, it has been challenging to explain howobserved community-wide patterns, such as the inverse relationship betweenpopulation abundance density and body size, can be unified under boththeories. Here, we provide the foundation for a tractable, scalable, and extend-able framework to study the coexistence of resource-mediated competingpopulations as a function of their body size. For a given thermal domain andresponse, this integration reveals that the metabolically predicted 1/4 powerdependence of carrying capacity of biomass density on body size can be under-stood as the average distribution of carrying capacities across feasible environ-mental conditions, especially for large communities. In line with empiricalobservations, our integration predicts that such average distribution leads tocommunities in which population biomass densities at equilibrium are inde-pendent from body size, and consequently, population abundance densitiesare inversely related to body size. This integration opens new opportunities toincrease our understanding of how metabolic scaling relationships at thepopulation level can shape processes at the community level under changingenvironments.