Figure 2. Alternative pathways, with and without [PSI⁺], leading to the same readthrough adaptation.

Adaptation in environment 2 can proceed either via: (1) [PSI⁺] appearance followed by point mutation at agp loci (genetic assimilation) and finally reversion to [psi ⁻] (left) and (2) direct adaptation at agp loci without involvement of [PSI⁺] (right). The fitness of an individual is given to the right of its genotype, calculated using s ₂ = 0.001. Only homozygous states are shown because inbreeding quickly leads to homozygosity. The genetic assimilation pathway typically occurs more often because [PSI⁺] individuals appear far more often than [psi⁻] individuals who carry the “+” allele at both agp loci.