Growth tradeoffs produce complex microbial communities without direct interactions

Michael Manhart and Eugene I. Shakhnovich

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Received: 15th February 18

The distribution of fitness effects for mutations is often believed to be key to predicting microbial evolution. However, fitness effects alone may be insufficient to predict evolutionary dynamics if mutations produce nontrivial ecological effects which depend on the composition of the population. Here we show that variation in multiple growth traits, such as lag times and growth rates, creates higher-order effects such the relative competition between two strains is fundamentally altered by the presence of a third strain. These effects produce a range of ecological phenomena: an unlimited number of strains can coexist, potentially with a single keystone strain stabilizing the community; strains that coexist in pairs do not coexist all together; and the champion of all pairwise competitions may not dominate in a mixed community. This occurs with competition for only a single finite resource and no other interactions. Since variation in multiple growth traits is ubiquitous in microbial populations due to pleiotropy and non-genetic variation, these higher-order effects may also be widespread, especially in laboratory ecology and evolution experiments. Our results underscore the importance of considering the distribution of ecological effects from mutations in predicting microbial evolution.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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