Digest: Investigating reproductive isolation in test tubes

Reproductive isolation can result from incompatibilities between mutations that arise in different individuals. Wang and Cooper examined this mechanism of postzygotic isolation in Escherichia coli experimentally evolved in either glucose or lactose. They formed recombinants from parents evolved in the same or different environments. Both same-environment and different-environment recombinants had lower fitness than the null expectation, but with important exceptions. These results indicate that the development of reproductive isolation is complex and results from incompatibilities that arise when populations are selected in either the same or different environment.