Figure 6. Simulations for rare mutations in combination with fast switching, where the number of individuals divided by 200 is plotted versus time.

(a) The mutant phenotype p₂ has a negative initial growth rate but can switch to p₁ which has a positive one. The fitness of the genotype g′ is positive. (b) The fitness of the mutant genotype g′ is positive, although each phenotype has a negative initial growth rate. This is possible because an outgoing switch is a loss of a particle for a phenotype, but not for the whole genotype.