Direct fitness responses of replicate populations within each group after 1000 and 2000 generations of experimental evolution. All fitness values are expressed relative to the common ancestor. Each point is the mean of four assays performed in the same experimental blocks. Lines connect the same populations measured at 1000 and 2000 generations.
Cooper and Lenski BMC Evolutionary Biology 2010 10:11 doi:10.1186/1471-2148-10-11