Data from: Parallel emergence of negative epistasis across experimental lineages

Epistatic interactions can impact evolutionary phenomena%2C particularly the process of adaptation. Here%2C we leverage four parallel experimentally evolved lineages to study the emergence and trajectories of epistatic interactions in the social bacterium Myxococcus xanthus. A social gene %28pilA%29 necessary for effective group swarming had been deleted from the common ancestor of these lineages. During selection for competitiveness at the leading edge of growing colonies%2C two lineages evolved qualitatively novel mechanisms for swarming on agar%2C whereas the other two lineages evolved relatively small increases in swarming. By reintroducing pilA into different genetic backgrounds along the four lineages%2C we tested whether parallel lineages showed similar patterns of epistasis. In particular%2C we tested whether any patterns of epistasis between accumulating mutations and pilA were unique to the emergence of the two novel evolved phenotypes%2C or rather were due to common epistatic structure across all lineages arising from the generic fixation of mutations. Our analysis reveals the rapid parallel emergence of negative epistasis across all lineages. Further%2C the pilA effect on motility is negatively correlated with the mean phenotypic response to selection. These parallel negative epistatic interactions suggest all four lineages increased fitness by mechanisms involving genetic co-option of the defunct ancestral motility system.