Correlations between the evolutionary rates of mouse enhancers and enhancer properties: the tissue-specificity of the enhancers (A, D), essentiality of the adjacent gene (B, E), and the expression level of the adjacent gene (C, F). Evolutionary rates are represented by D (A-C) or D/d4 (D-F). Spearman's rank correlation coefficient is (C) 0.040 (P <10-3) and (F) 0.046 (P <10-4) for the unbinned data. The values of upper quartile, median, and lower quartile are indicated in each box, whereas the bars outside the box indicate semi-quartile ranges. Pairwise comparisons showing significant differences in D or D/d4 are connected with gray lines (*0.01<P≦0.05 and ***P≦0.001 by Mann-Whitney U test).