Data from: Adaptation of Escherichia coli to glucose promotes evolvability in lactose

The selective history of a population can influence its subsequent
evolution, an effect known as historical contingency. We previously
observed that five of six replicate populations that were evolved in a
glucose-limited environment for 2,000 generations, then switched to
lactose for 1,000 generations, had higher fitness increases in lactose
than populations started directly from the ancestor. To test if selection
in glucose systematically increased lactose evolvability, we started 12
replay populations—six from a population subsample and six from a single
randomly selected clone—from each of the six glucose-evolved founder
populations. These replay populations and 18 ancestral populations were
evolved for 1,000 generations in a lactose-limited environment. We found
that replay populations were initially slightly less fit in lactose than
the ancestor, but were more evolvable, in that they increased in fitness
at a faster rate and to higher levels. This result indicates that
evolution in the glucose environment resulted in genetic changes that
increased the potential of genotypes to adapt to lactose. Genome
sequencing identified four genes—iclR, nadR, spoT and rbs—that were
mutated in most glucose-evolved clones and are candidates for mediating
increased evolvability. Our results demonstrate short-term selective costs
during selection in one environment can lead to changes in evolvability
that confer longer-term benefits.