All Sizes Fit the Red Queen

Indrė Žliobaitė,Mikael Fortelius

doi:10.1017/pab.2020.35

Abstract

AbstractThe Red Queen's hypothesis portrays evolution as a never-ending competition for expansive energy, where one species’ gain is another species’ loss. The Red Queen is neutral with respect to body size, implying that neither small nor large species have a universal competitive advantage. Here we ask whether, and if so how, the Red Queen's hypothesis really can accommodate differences in body size. The maximum population growth in ecology clearly depends on body size—the smaller the species, the shorter the generation length, and the faster it can expand given sufficient opportunity. On the other hand, large species are more efficient in energy use due to metabolic scaling and can maintain more biomass with the same energy. The advantage of shorter generation makes a wide range of body sizes competitive, yet large species do not take over. We analytically show that individuals consume energy and reproduce in physiological time, but need to compete for energy in real time. The Red Queen, through adaptive evolution of populations, balances the pressures of real and physiological time. Modeling competition for energy as a proportional prize contest from economics, we further show that Red Queen's zero-sum game can generate unimodal hat-like patterns of species rise and decline that can be neutral in relation to body size.

Highlights

One of the most influential evolutionary theories—the Red Queen’s hypothesis (Van Valen 1973, 1980)—portrays species evolution as a never-ending competition for expansive energy,* where one species’ gain inevitably results in a corresponding loss for other species
We model the relationships between individual evolutionary advantage and gain in expansive energy by a population of species as a proportional prize contest known from economics (Cason et al 2020), in which rewards are shared in proportion to performance
As we argue, α does not depend on body mass, the rest of the equation does not depend on body mass

Summary

Introduction

One of the most influential evolutionary theories—the Red Queen’s hypothesis (Van Valen 1973, 1980)—portrays species evolution as a never-ending competition for expansive energy,* where one species’ gain inevitably results in a corresponding loss for other species. If unlimited energy for expansion is available, generation length (time) is the limiting factor for population growth This is well known from ecology, where theory and empirical observations suggest that the maximum population growth rate scales as rgmraoxwth ∝ M−0.25 (Fenchel 1974; Brown 1995), where M is body mass. Our step is to model mechanisms of how an evolutionary advance translates to expansive energy and analyze conditions under which the acquired expansive energy at the population level may or may not depend on body size This question is important for understanding conditions under which large and small species can compete as equals, despite individuals having different daily energy efficiencies (metabolism).

Conclusion

Findings

Literature Cited