Enabling evolvability to evolve

Evolvability, or the capacity to generate adaptive phenotypic variation, can itself evolve in response to selection (1). Species that evolve too slowly may be unable to adapt to environmental change and are more likely to go extinct than faster-evolving species. Yet what it takes to get evolvability to evolve, in nature or in the lab, has remained puzzling. For example, many generations might be needed for natural selection to change a species’ ability to adapt. Higher evolvability can result in lower heritability, a cornerstone of natural selection’s ability to act, and the same degree of evolvability might not suit all traits equally. On page 840 of this issue, Barnett et al. (2) describe how experimental evolution can yield increased evolvability by localized hypermutation in populations of bacteria exposed to an alternating selection regime, akin to the regularly fluctuating conditions that pathogenic bacteria experience moving from one host to another.