Figure 12. Outdegree distribution of assembled GRNs that evolved under various C_mut levels.

Horizontal and vertical axes in each panel show the outdegree (the number of regulatory interactions that depart from a gene) and the frequency, respectively. Note that the both horizontal and vertical axes are shown logarithmically to demonstrate the scale-free character of the distribution. Different rows and columns show the different conditions of phenotypic selection and the different values of C_mut, respectively. Lines in each panel indicate the regression of the plot to the Power law distribution (red), exponential distribution (blue) and Poisson distribution (green). Regression was estimated by a nonlinear least-square method. To judge the goodness of the regression, Akaike's information criterion (AIC) was used, and the regression that showed the smallest value of AIC was drawn as a thick line. POW, EXP and POI in each panel indicate the differences between AIC value of the best regression model and those of power-law (scale-free), exponential and poisson distributions, respectively.