Identical mutations in separate populations

Or similar changes in the environment favor similar (and some times identical) mutations.

1. Grow E. coli in medium with glucose and acetate.
2. See how specialized populations emerge.
3. Sequence.
4. Observe parallel emergent changes in independent populations.

Herron, M. D. & Doebeli, M. 

Parallel Evolutionary Dynamics of Adaptive Diversification inEscherichia coli

PLoS Biol. 11, e1001490 (2013).