Long-Term Experimental Evolution in Escherichia coli. I. Adaptation and Divergence During 2,000 Generations

@article{Lenski1991LongTermEE,
  title={Long-Term Experimental Evolution in Escherichia coli. I. Adaptation and Divergence During 2,000 Generations},
  author={Richard E. Lenski and M. Rose and Suzanne C. Simpson and Scott C. Tadler},
  journal={The American Naturalist},
  year={1991},
  volume={138},
  pages={1315 - 1341}
}
We assess the degree to which adaptation to a uniform environment among independently evolving asexual populations is associated with increasing divergence of those populations. In addition, we are concerned with the pattern of adaptation itself, particularly whether the rate of increase in mean fitness tends to decline with the number of generations of selection in a constant environment. The correspondence between the rate of increase in mean fitness and the within-population genetic variance… Expand
LONG‐TERM EXPERIMENTAL EVOLUTION IN ESCHERICHIA COLI. VII. MECHANISMS MAINTAINING GENETIC VARIABILITY WITHIN POPULATIONS
  • S. Elena, R. Lenski
  • Biology, Medicine
  • Evolution; international journal of organic evolution
  • 1997
Six replicate populations of the bacterium Escherichia coli were propagated for more than 10,000 generations in a defined environment. We sought to quantify the variation among clones within theseExpand
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An asymmetric pattern of correlated responses suggests that small changes in the environment can have profound effects on adaptation and divergence. Expand
Long‐term experimental evolution in Escherichia coli. V. Effects of recombination with immigrant genotypes on the rate of bacterial evolution
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The estimated recombination rate was too low to explain the observed rate of genetic change, either alone or in combination with hitchhiking effects, but the method for estimating fitness relative to a common competitor might have underestimated the rate of adaptive evolution in the treatment populations. Expand
Genetic divergence and fitness convergence under uniform selection in experimental populations of bacteria.
TLDR
It is suggested that genetic diversity developed because selection promoted any changes directing cell activity toward a higher maximum growth rate, and near the limit of adaptation, epistasis levels off the fitnesses of genetically variable clones. Expand
Long-Term Dynamics of Adaptation in Asexual Populations
TLDR
It is demonstrated that even after 50,000 generations over 20 years, gains in fitness show no evidence of leveling off, and mean fitness appears to increase without bound, consistent with a power law. Expand
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It is hypothesized that pleiotropy involving the selected alleles, rather than random genetic drift of alleles at other loci, was the major cause of the variation among the derived genotypes in fitness on these other sugars. Expand
Constraints on adaptation of Escherichia coli to mixed‐resource environments increase over time
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The results indicate that costs of generalism are prevalent, but may influence evolutionary trajectories only after a period of cost‐free adaptation. Expand
Fitness evolution and the rise of mutator alleles in experimental Escherichia coli populations.
TLDR
This work identified the mutations responsible for the high mutation rates and shows that their rate of substitution in all three populations was too rapid to be accounted for simply by genetic drift, strongly supporting the conclusion that mutator alleles fixed by hitchhiking with beneficial mutations at other loci. Expand
Long-Term Experimental Evolution in Escherichia coli. II. Changes in Life-History Traits During Adaptation to a Seasonal Environment
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The independently derived genotypes are somewhat more variable in these life-history traits than in their relative fitnesses, which indicates that they acquired different genetic adaptations to the seasonal environment. Expand
High mutation rates limit evolutionary adaptation in Escherichia coli
TLDR
This work demonstrates that the mutation rate changes the global balance between deleterious and beneficial mutational effects on fitness, and suggests that this tipping point already occurs at the modest mutation rates that are found in the wild. Expand
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