Clonal selection prevents tragedy of the commons when neighbors compete in a rock-paper-scissors game

TL;DR

This study investigates how clonal selection influences species coexistence in a rock-paper-scissors model, showing that selective pressures can prevent ecosystem collapse by stabilizing growth rates through group selection.

Contribution

It demonstrates that clonal selection mechanisms can stabilize cyclic competition systems, preventing tragedy of the commons in ecosystems with evolving species.

Findings

Mutations in all species lead to perpetual arms races without dominance.

Selective mutation in two species causes ecosystem collapse due to unchecked aggression.

Single-species mutation stabilizes growth rates via group selection, preventing collapse.

Abstract

The rock-paper-scissors game is a model example of the on-going cyclic turnover typical of many ecosystems, ranging from the terrestrial and aquatic to the microbial. Here we explore the evolution of a rock-paper-scissors system where three species compete for space. The species are allowed to mutate and change the speed by which they invade one another. In the case when all species have similar mutation rates, we observe a perpetual arms race where no single species prevails. When only two species mutate, their aggressions increase indefinitely until the ecosystem collapses and only the non-mutating species survives. Finally we show that when only one species mutates, group selection removes individual predators with the fastest growth rates, causing the growth rate of the species to stabilize. We explain this group selection quantitatively.