New paper from Andreas Wagner & colleagues that touches on topics of perennial interest (and debate) here.
Here is the abstract in case the paper is paywalled:
Cryptic genetic variation can facilitate adaptation in evolving populations. To elucidate the underlying genetic mechanisms, we used directed evolution in Escherichia coli to accumulate variation in populations of yellow fluorescent proteins and then evolved these proteins toward the new phenotype of green fluorescence. Populations with cryptic variation evolved adaptive genotypes with greater diversity and higher fitness than populations without cryptic variation, which converged on similar genotypes. Populations with cryptic variation accumulated neutral or deleterious mutations that break the constraints on the order in which adaptive mutations arise. In doing so, cryptic variation opens paths to adaptive genotypes, creates historical contingency, and reduces the predictability of evolution by allowing different replicate populations to climb different adaptive peaks and explore otherwise-inaccessible regions of an adaptive landscape.
Here is a popular summary as well:
Tales from the crypt(ic)
Adaptation through natural selection requires inherited changes in an organism’s phenotype. However, neutral or “cryptic” mutations—changes in genotype that do not affect phenotype—can influence adaptation outcomes, because genotype-to-phenotype mapping is inherently dependent on context. The phenotypic consequence of a mutation might change as a result of interactions either with other mutations in the genome (epistasis) or with the physical environment [a genotype-by-environment (G×E) interaction]. On page 347 of this issue, Zheng et al. ( 1 ) demonstrate that the accumulation of mutations that yield neutral changes in a protein promotes faster adaptation in an environment selecting for a new function, and that this effect requires the combined impact of epistasis and G×E interactions.