Bioenergetic trophic trade-offs determine mass-dependent extinction thresholds across the Cenozoic

TL;DR

This paper presents a theoretical model linking bioenergetic trade-offs to body size limits and extinction thresholds in terrestrial mammalian food chains over the Cenozoic, highlighting size-dependent ecological constraints.

Contribution

It introduces a novel bioenergetic framework for three-level trophic interactions that explains size-dependent stability and extinction thresholds in mammalian communities.

Findings

Predator-prey interactions create size-related instabilities.

Feasibility range for carnivore size is 40-110 kg.

Larger carnivores benefit from dietary generalization, but decline at megapredator sizes.

Abstract

Body size drives the energetic demands of organisms, constraining trophic interactions between species and playing a significant role in shaping the feasibility of species' populations in a community. On macroevolutionary timescales, these demands feed back to shape the selective landscape driving the evolution of body size and diet. We develop a theoretical framework for a three-level trophic food chain -- typical for terrestrial mammalian ecosystems -- premised on bioenergetic trade-offs to explore mammalian population dynamics. Our results show that interactions between predators, prey, and external subsidies generate instabilities linked to body size extrema, corresponding to observed limits of predator size and diet. These instabilities generate size-dependent constraints on coexistence and highlight a feasibility range for carnivore size between 40 to 110 kg, encompassing the mean body size of terrestrial Cenozoic hypercarnivores. Finally, we show that predator dietary generalization confers a selective advantage to larger carnivores, which then declines at megapredator body sizes, aligning with diet breadth estimates for contemporary and Pleistocene species. Our framework underscores the importance of understanding macroevolutionary constraints through the lens of ecological pressures, where the selective forces shaping and reshaping the dynamics of communities can be explored.