Figure 1.

Genetic exchanges reduce the frequency of mutator fixation, although faster adaptation is always occurring in a mutator background. (A) Frequency of 100-fold mutator allele fixation (white) and contribution (gray) in a large population (10⁹ bacteria) (1,000 simulations per point). (B) Difference in adaptation times between mutator and antimutator backgrounds in large populations (over 200 simulations). ○, The mean adaptation time of populations with a fixed low mutation rate; □, populations with a fixed high mutation rate (100-fold higher than the previous). ▴, The mean adaptation time of populations with an initially low mutation rate that could possibly fix a 100-fold mutator during adaptation.