Figure 5. Decomposition of robustness.

Robustness due to stable individuals is the sum of the products between the frequency and the average phenotypic distance of the mutational events described in Fig. 4A. Therefore they can be used to decompose robustness. (A) Relative composition of the frequencies of each mutation type. They were measured as the differences between final and initial generations in the simulations for each of the classified mutational events (see Materials and Methods). Silent mutations dominate in almost all cases, especially at low specificity gap (γ) and URR lengths (L). Silent mutations are found at the extreme of local-sequence level changes (Fig. 4B). (B) Fraction of local-sequence and network-architecture level changes. Local changes were calculated as the fraction of the total robustness change assuming constant frequency of silent mutations (see Materials and Methods). The length of the URRs (in base pairs) is indicated on top of each bar in both graphs.