Evolutionary capacitance may be favored by natural selection

Evolutionary capacitors phenotypically reveal a stock of cryptic genetic variation in a reversible fashion. The sudden and reversible revelation of a range of variation is fundamentally different from the gradual introduction of variation by mutation. Here I study the invasion dynamics of modifiers of revelation. A modifier with the optimal rate of revelation m_opt has a higher probability of invading any other population than of being counterinvaded. m_opt varies with the population size N and the rate θ at which environmental change makes revelation adaptive. For small populations less than a minimum cutoff N_min, all revelation is selected against. N_min is typically quite small and increases only weakly, with θ^-1/2. For large populations with N > 1/θ, m_opt is ∼1/N. Selection for the optimum is highly effective and increases in effectiveness with larger N ≫ 1/θ. For intermediate values of N, m_opt is typically a little less than θ and is only weakly favored over less frequent revelation. The model is analogous to a two-locus model for the evolution of a mutator allele. It is a fully stochastic model and so is able to show that selection for revelation can be strong enough to overcome random drift.