Fitness trajectory measured relative to clones from five time-points. (A) Each line shows the fitness trajectory of the Ara-1 population measured relative to one of five clones bearing a neutral marker. The clones are the ancestor and isolates from generations 5,000, 10,000, 15,000 and 20,000. Each competition was replicated three-fold, and error bars are standard errors. (B) The same data ln-transformed.