Interesting new paper about the evolution of cooperation. It’s a classic question in evolution: how can mutualistic cooperation emerge, given the likely (or certain) presence of cheaters? This new paper explores the question in bacteria, and they find evidence that cooperation emerges more readily in structured environments, i.e., small spaces. This had been proposed before as a potential solution to the cheating problem, but apparently there was little or no strong experimental support for the idea. That was the goal of the paper.
Reciprocal Fitness Feedbacks Promote the Evolution of Mutualistic Cooperation
Summary: Mutually beneficial interactions are ubiquitous in nature and have played a pivotal role for the evolution of life on earth. However, the factors facilitating their emergence remain poorly understood. Here, we address this issue both experimentally and by mathematical modeling using cocultures of auxotrophic strains of Escherichia coli, whose growth depends on a reciprocal exchange of amino acids. Coevolving auxotrophic pairs in a spatially heterogeneous environment for less than 150 generations transformed the initial interaction that was merely based on an exchange of metabolic byproducts into a costly metabolic cooperation, in which both partners increased the amounts of metabolites they produced to benefit their corresponding partner. The observed changes were afforded by the formation of multicellular clusters, within which increased cooperative investments were favored by positive fitness feedbacks among interacting genotypes. Under these conditions, non-cooperative individuals were less fit than cooperative mutants. Together, our results highlight the ease with which mutualistic cooperation can evolve, suggesting similar mechanisms likely operate in natural communities.
The paper has a nice video abstract, and access is free for the next few weeks. Their experiment was ambitious, and the paper is nicely written so non-specialists should be able to enjoy at least the Introduction. For the 5 or 6 people here who are curious about science.