image: Antagonistic epistasis. Bacteria adapt to a laboratory environment by acquiring beneficial mutations. Khan et al. and Chou et al. identified the mutations that accrued in an adapted strain, and measured their fitness benefits (growth advantage compared to the ancestor). The mutations conferred smaller marginal benefits in combination than they did individually. This antagonistic epistasis causes progressively slower rates of adaptation over time. This image relates to two papers that appeared in the June 3, 2011, issue of Science, published by AAAS. One study, by H.-H. Chou of Harvard University in Cambridge, MA, and colleagues was titled, "Diminishing Returns Epistasis Among Beneficial Mutations Decelerates Adaptation." The other study, by A.I. Khan of University of Houston in Houston, Texas, and colleagues, was titled, "Negative Epistasis Between Beneficial Mutations in an Evolving Bacterial Population." This image is from the related perspective titled, "In Evolution, the Sum is Less than Its Parts," by Sergey Kryazhimskiy. view more
Credit: [Image adapted by P. Huey/<i>Science</i> © 2011 AAAS]