environmental stress. 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. These observations are compatible with [PSI+] acting as an evolutionary capacitor in the wild. Similar transient increases in error rates can evolve emergently in the absence of a "widget" like [PSI+]. The primary advantage of a [PSI+]-like widget is to facilitate the subsequent evolution of lower error rates once genetic assimilation has occurred. Gene knockouts Evolutionary capacitance may also be a general feature of complex gene networks, and can be seen in simulations of gene knockouts. A screen of all gene knockouts in yeast found that many act as phenotypic stabilizers. Knocking out a regulatory protein such as a chromatin regulator may lead to more effective capacitance than knocking out a metabolic enzyme. Facultative sex Recessive mutations can be thought of as cryptic when they are present overwhelmingly in heterozygotes rather than homozygotes. Facultative sex that takes the form of selfing can act as an evolutionary capacitor in a primarily asexual population by creating homozygotes. 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. See also Canalization (genetics) Epigenetics Preadaptation Susan Lindquist References Evolutionary biology Extended evolutionary synthesis Selection