Local dispersal promotes biodiversity in a real-life game of rock–paper–scissors

Abstract

One of the central aims of ecology is to identify mechanisms that maintain biodiversity. Numerous theoretical models have shown that competing species can coexist if ecological processes such as dispersal, movement, and interaction occur over small spatial scales. In particular, this may be the case for non-transitive communities, that is, those without strict competitive hierarchies. The classic non-transitive system involves a community of three competing species satisfying a relationship similar to the children's game rock-paper-scissors, where rock crushes scissors, scissors cuts paper, and paper covers rock. Such relationships have been demonstrated in several natural systems. Some models predict that local interaction and dispersal are sufficient to ensure coexistence of all three species in such a community, whereas diversity is lost when ecological processes occur over larger scales. Here, we test these predictions empirically using a non-transitive model community containing three populations of Escherichia coli. We find that diversity is rapidly lost in our experimental community when dispersal and interaction occur over relatively large spatial scales, whereas all populations coexist when ecological processes are localized.

Evolution of cooperation and control of cheating in a social microbe

“…This is particularly true for microbes, wherein the structured environments necessary for cooperation have been discovered to be pervasive (10,19,20). Microbes are particularly affected by the actions of their neighbors, because many functions that are internal in multicellular organisms are external in single-celled organisms.…”

Competing associations in bacterial warfare with two toxins

“…Recent research on bacteriocins (Chao and Levin, 1981;Durrett and Levin, 1997;Iwasa et al, 1998;Pagie and Hogeweg, 1999;Nakamaru and Iwasa, 2000;Cza´ra´n et al, 2002;Kerr et al, 2002) suggests that competitive cycles are in fact the rule rather than the exception in communities of microorganisms.…”

“…Thus, based on metabolic efficiency alone, i.e., in terms of resource competition, S should be dominant over both R and K, and R would be superior to K. This line of resource-competitive hierarchy is bent to form a cycle by the interference-competitive dominance of K over S due to toxic killing. In other words, S, R and K play the Rock-Scissors-Paper game which is known to be stable in a spatial setting: in a lattice model implementation of the game the three strains maintain coexistence in a spatially dynamic pattern (Tainaka, 1988;Kerr et al, 2002;Cza´ra´n et al, 2002;Kirkup and Riley, 2004).…”

Natural Selection as a Population-Level Causal Process

“…In other words, none of the three is superior to the other two; each is superior to one, but inferior to another. Kerr et al ([2002]) study a population of Escherichia coli that manifests this non-transitivity. The population contains three types of cells: 1) colicinogenic cells (C), which are cells that can produce a toxin, colicin; 2) sensitive cells (S), which are cells that can be killed by the colicin; and 3) resistant cells (R), which are immune to the colicin.…”

“…Non-transitive populations can be compared to the children's game of 'Rock, Paper, Scissors' where rock crushes scissors, scissors cut paper, but paper covers rock (Kerr et al [2002]). In other words, none of the three is superior to the other two; each is superior to one, but inferior to another.…”