The dynamics of molecular evolution over 60,000 generations

Area of Science:

• Evolutionary biology
• Microbial evolution
• Genomics

Background:

• Evolutionary outcomes depend on mutation dynamics.
• Observing long-term genomic evolution is challenging.

Purpose of the Study:

• To analyze molecular evolution dynamics in experimental populations.
• To investigate adaptation over extended periods and entire genomes.

Main Methods:

• Whole-genome metagenomic sequencing of twelve Escherichia coli populations.
• Sampling at 500-generation intervals over 60,000 generations.

Main Results:

• Signatures of rapid adaptation persisted throughout the experiment.
• Multiple beneficial variants competed simultaneously.
• Ecological-evolutionary interactions led to clade coexistence and ongoing evolution.
• Epistasis and historical contingency altered selection targets over time.

Conclusions:

• Long-term adaptation in a constant environment is complex and dynamic.
• The targets of natural selection can shift during adaptation.
• Stochastic processes and ecological interactions shape evolutionary trajectories.