Evolutionary capacitance
But when the system is disturbed (perhaps by stress), robustness breaks down, and the variation has phenotypic effects and is subject to the full force of natural selection.
After that, the rest of variation, most of which is presumably deleterious, can be switched off, leaving the population with a newly evolved advantageous trait, but no long-term handicap.
These reactions or interactions may be of no consequence to current fitness but under altered conditions, may provide the starting point for adaptive evolution.
[9] In populations exposed only to ampicillin, such mutations may be present in a minority of members since there is not fitness cost (i.e. are within the neutral network).
This represents cryptic genetic variation since if the population is newly exposed to cefotaxime, the minority members will exhibit some resistance.
It has been proposed that the presence of chaperones may, by providing additional robustness to errors in folding, allow the exploration of a larger set of genotypes.
More recent evidence suggests that these data might be explained by new mutations caused by the reactivation of formally dormant transposable elements.
[19] In yeast, more stop codon disappearances are in-frame, mimicking the effects of [PSI+], than would be expected from mutation bias or than are observed in other taxa that do not form the [PSI+] prion.
[21] The primary advantage of a [PSI+]-like widget is to facilitate the subsequent evolution of lower error rates once genetic assimilation has occurred.
The majority of the variation in protein expression is attributable to trans effects, suggesting that trans-regulatory processes are strongly involved in canalization.
The confidence that a specific gene acts as a phenotypic capacitor is correlated with the number of protein-protein interactions observed for its expressed protein.
[25] The mechanism of phenotypic capacitor genes in yeast appears to be closely related to the modalities of functional redundancy at various levels of the genome.
In general the phenotypic capacitors identified by knockouts in yeast are genes expressed in several key regulatory areas which, while non-lethal when removed, do not have enough redundancy to maintain complete functionality.
Facultative sex that takes the form of selfing can act as an evolutionary capacitor in a primarily asexual population by creating homozygotes.
[27] Facultative sex that takes the form of outcrossing can act as an evolutionary capacitor by breaking up allele combinations with phenotypic effects that normally cancel out.
