Convergence and Divergence in a Long-Term Experiment with Bacteria.

Area of Science:

• Evolutionary biology
• Microbial evolution
• Experimental evolution

Background:

• Quantifying evolutionary convergence is challenging.
• Designed experiments with replicate populations offer a solution.
• A long-term experiment with Escherichia coli (E. coli) provides a unique dataset.

Purpose of the Study:

• To review a long-term experiment investigating evolutionary convergence and divergence.
• To analyze various traits including fitness, morphology, and genomic changes.
• To understand the interplay between convergence and divergence in replicate lineages.

Main Methods:

• Evolution of 12 replicate E. coli populations for over 65,000 generations.
• Analysis of competitive fitness, correlated responses, cell morphology, resource utilization, mutation rates, genomic changes, and polymorphisms.
• Comparison of evolutionary trajectories across replicate populations.

Main Results:

• Observed both convergence and divergence in replicate populations.
• Identified complex patterns, including concordance in evolutionary direction with quantitative variation.
• Demonstrated that traits can exhibit divergence on one timescale and convergence on another.

Conclusions:

• Experimental evolution with replicate lineages is a powerful tool for studying evolutionary convergence.
• Evolutionary processes in nature are complex, mirroring findings from experimental systems.
• Understanding the balance between convergence and divergence is key to evolutionary studies.