Fitness Landscape & Epistasis

Evolution navigating rugged adaptive peaks
Epistasis ε 0.80
Roughness σ 0.60
Population size 5
Click to place population
Epistasis means mutations interact: the effect of gene A depends on what gene B is doing. Low epistasis → smooth landscape (single peak). High epistasis → rugged landscape (many local optima). Evolution greedily climbs fitness peaks but can get trapped. Recombination (sex) helps escape by combining distant genotypes. NK model (Kauffman 1993): N genes each interacting with K others — K=0 smooth, K=N-1 maximally rugged.