Spatial self-organization favors heterotypic cooperation over cheating

Babak Momeni,Adam James Waite,Wenying Shou

doi:10.7554/elife.00960

Abstract

Heterotypic cooperation-two populations exchanging distinct benefits that are costly to produce-is widespread. Cheaters, exploiting benefits while evading contribution, can undermine cooperation. Two mechanisms can stabilize heterotypic cooperation. In 'partner choice', cooperators recognize and choose cooperating over cheating partners; in 'partner fidelity feedback', fitness-feedback from repeated interactions ensures that aiding your partner helps yourself. How might a spatial environment, which facilitates repeated interactions, promote fitness-feedback? We examined this process through mathematical models and engineered Saccharomyces cerevisiae strains incapable of recognition. Here, cooperators and their heterotypic cooperative partners (partners) exchanged distinct essential metabolites. Cheaters exploited partner-produced metabolites without reciprocating, and were competitively superior to cooperators. Despite initially random spatial distributions, cooperators gained more partner neighbors than cheaters did. The less a cheater contributed, the more it was excluded and disfavored. This self-organization, driven by asymmetric fitness effects of cooperators and cheaters on partners during cell growth into open space, achieves assortment. DOI: http://dx.doi.org/10.7554/eLife.00960.001.

Highlights

Cooperation, providing a benefit available to others at a cost to self, has been postulated to drive major transitions in evolution (Maynard Smith and Szathmary, 1998)
In this study, using engineered yeast strains and mathematical models devoid of possibilities for partner choice, we examined how through partner fidelity feedback heterotypic cooperation between microbes may be protected against cheaters
The mechanism for how partner fidelity feedback unfolds in a spatial environment is not well understood

Summary

Introduction

Cooperation, providing a benefit available to others at a cost to self, has been postulated to drive major transitions in evolution (Maynard Smith and Szathmary, 1998). Cooperators R←→LA are favored over cheaters C←L . In the absence of supplements, cooperator R←→LA and the competitively superior cheater C←L competed for the lysine supplied by the heterotypic cooperative partner (partner) G←→AL (Figure 1B, ‘Co&Ch’).

Results

Conclusion