Mutational robustness

Mutational robustness describes the extent to which an organism's phenotype remains constant in spite of mutation. Selection can directly induce the evolution of mutational robustness only when mutation rates are high and population sizes are large. However, there may be considerable indirect selection for mutational robustness and a correlated response to selection for robustness against non-genetic changes (i.e. changes in the environment). The conditions under which selection could act to directly increase mutational robustness are extremely restrictive, and for this reason, such selection is thought to be limited to only a few viruses and other microbes having large population sizes. Mutational robustness is thought to be one driver for theoretical viral quasispecies formation.