Nov 15, 2014

The impact of macroscopic epistasis on long-term evolutionary dynamics

Genetics
Benjamin H Good, Michael M Desai

Abstract

Genetic interactions can strongly influence the fitness effects of individual mutations, yet the impact of these epistatic interactions on evolutionary dynamics remains poorly understood. Here we investigate the evolutionary role of epistasis over 50,000 generations in a well-studied laboratory evolution experiment in Escherichia coli. The extensive duration of this experiment provides a unique window into the effects of epistasis during long-term adaptation to a constant environment. Guided by analytical results in the weak-mutation limit, we develop a computational framework to assess the compatibility of a given epistatic model with the observed patterns of fitness gain and mutation accumulation through time. We find that a decelerating fitness trajectory alone provides little power to distinguish between competing models, including those that lack any direct epistatic interactions between mutations. However, when combined with the mutation trajectory, these observables place strong constraints on the set of possible models of epistasis, ruling out many existing explanations of the data. Instead, we find that the data are consistent with a "two-epoch" model of adaptation, in which an initial burst of diminishing-returns epis...Continue Reading

  • References44
  • Citations12

References

  • References44
  • Citations12

Mentioned in this Paper

Patterns
Epoch
Alkalescens-Dispar Group
Environment
In Vitro Molecular Evolution
Adaptation
Drug Interactions
Sequence Determinations, DNA
Deviation, Epistatic
Escherichia coli

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