Many ways to stay in the game: Individual variability maintains high biodiversity in planktonic micro-organisms

TL;DR

This paper introduces a game-theoretic model demonstrating that intra-specific variability among micro-organisms promotes stable coexistence of many plankton species, addressing the Paradox of the Plankton.

Contribution

The paper presents a novel model showing that individual variability enables coexistence of numerous species, providing a new explanation for the paradox.

Findings

Up to 100 species can coexist over 10,000 generations in simulations.

Intra-specific variability allows even less competitive species to survive.

The model aligns with observed ecological variability like niche differentiation.

Abstract

In apparent contradiction to competition theory, the number of known, co-existing plankton species far exceeds their explicable biodiversity - a discrepancy termed the Paradox of the Plankton. We introduce a new game-theoretic model for competing micro-organisms in which one player consists of all organisms of one species. The stable points for the population dynamics in our model, known as strategic behavior distributions (SBDs), are probability distributions of behaviors across all organisms which imply a stable population of the species as a whole. We find that intra-specific variability is the key characteristic that ultimately allows co-existence because the outcomes of competitions between individuals with variable competitive abilities is unpredictable. Our simulations based on the theoretical model show that up to 100 species can coexist for at least 10000 generations, and that even small population sizes or species with inferior competitive ability can survive when there is intra-specific variability. In nature, this variability can be observed as niche differentiation, variability in environmental and ecological factors, and variability of individual behaviors or physiology. Therefore previous specific explanations of the paradox are consistent with and provide specific examples of our suggestion that individual variability is the mechanism which solves the paradox.