: population size at time after the onset of the stress.

: initial population size at the onset of the stress.

Mutation rate per individual per unit time.

Number of traits under stabilizing selection, or phenotypic dimensionality.

Variance of mutational effects: variance of the phenotypic effects of mutations, per trait, in a trait space scaled by the strength of stabilizing selection

Critical mutation rate below which the SSWM regime is valid.

-dimensional vector of (breeding values for) phenotype

optimal phenotype in a given environment

new environment

average phenotype of the ancestral population (before the onset of stress)

previous environment

Growth rate () and reproductive variance () of a given genotype, in the new environment.

Equation (1)

Maximum possible growth rate in the new environment.

Rate of decay of the ancestral phenotype in the new environment.

Cost of a mutation: selective disadvantage of the mutant, relative to the optimal phenotype, in the previous environment.

Harmonic mean of the cost among de novo mutations with scaled growth rate in the new environment

Equation (3)

Growth rate of a genotype, in the new environment, scaled by .

Probability density function of among random single step mutations

Equation (2)

Rate of decay scaled by

Alternative measure of

(Equation (6))

Effective stress level

Equation (6)

Characteristic stress level () or decay rate () beyond which ER probability drops below

Equation (8)

Function driving the dependence of rescue probabilities on stress levels.

Equations (7a) and (7b)

rate of rescue from de novo mutations scaled by

Equations (5), (7a) and (7b)

corresponding approximation when

rate of rescue from standing variance scaled by

Equations (5) and (10)

corresponding approximation when

Probability of rescue.

Proportion of rescue events caused by standing variants