FIG 2.

Frequency of plasmid variants in the populations during the experimental evolution. The frequencies of pB1000 variants in the different populations estimated during the experimental evolution in the absence (A) or presence (B) of antibiotic pressure are shown. The frequency of each allele is represented; therefore, when one of the alleles progresses to fixation (100% frequency), the other allele disappears from the population (0% frequency). The five populations in each treatment initially carried both plasmid variants and are represented by five different shades of blue lines (variant C3880) and green dotted lines (variant A3880), as indicated. Note that in the presence of ampicillin all the populations maintained both plasmid variants, whereas in the absence of ampicillin, 4 out of 5 populations completely lost one of the variants.