Figure 2. Phylogenetic inference of the evolutionary history of yeast pathway regulation from data simulated under an Ornstein-Uhlenbeck (OU) model.

(a), Data are as in Figure 1a except that expression measurements were simulated under an OU model in which the phylogeny-wide rate of regulatory evolution for each gene was drawn from an inverse-gamma distribution with , and the phylogeny-wide constraint parameter had a value of 10. (b), Data are as in Figure 1b except that expression measurements were simulated under an OU model in which the phylogeny-wide rate of regulatory evolution for each gene was drawn from an inverse-gamma distribution with , and the phylogeny-wide constraint parameter had the value indicated on the axis.