Figure 2
From: Adaptive evolution of transcription factor binding sites
Fitness landscapes and adaptive evolution for a pair of sites with cooperative binding. Genetic switch (left column), signal integration module (right column). (a,b) Fitness landscape F(r1, r2) without cooperativity (Îł = 0). (c,d) Fitness landscape. F(r1, r2) with cooperativity (Îł = 1). Next-nearest neighbour states (r1, r2) and 
of similar fitness are linked by compensatory mutations if the intermediate states (r1, 
) and (
, r2) have lower fitness. (e,f) Adaptive dynamics: ensemble averages 
and 
(thick lines), ensemble width given by 
(same for r2 and 
(thin lines); cf. fig. 1(e,f).