Fig 2.

Fitness increased in nitrogen-limited but not carbon-limited environments. Each bar represents the percent change in fitness for a clone isolated from an evolved population compared to its ancestor. All evolved clones were assayed in their evolutionary environment. Percent change was calculated from the mean relative fitness across three paired replicate competitions against a common competitor (REL607). Fitness under nitrogen limitation increased significantly (paired t-test, P < 10⁻⁶) following 1,000 generations of evolution in a nitrogen-limited environment (A). Fitness under carbon limitation did not change significantly (P = 0.173) following 1,000 generations of evolution in the same carbon-limited environment as the LTEE (B). Error bars show the range of the three replicate measurements for each population.