Fig. 1

An illustrative example of edge-removal mutations. a The original network G(V, A). b The mutant network G ^′(V, A ^′) by removal of I → B and A ⊣ I. It was observed that both networks G and G ^′ consist of three modules. Modularity and robustness values in G were 0.35799 and 0.88889, respectively, whereas those in G ^′ were 0.48347 and 0.74444, respectively. Therefore, the changes of the modularity and the robustness were positive (0.12548) and negative (−0.14445), respectively