Fig. 4

Direction and magnitude of natural selection acting on different flowering gene sets. Quantile boxplots (0.25, 0.75) show the distribution of Ka/Ks values for homologous gene pairs. The horizontal bar in each box indicates the median value. The upper and lower bars correspond to the upper and lower adjacent values 1.5-times outside the inter-quartile range. Outliers are plotted as discrete dots. Different letters indicate significantly different values (P < 0.01) as measured by Scheffé’s test. GM, gibberellin signaling and metabolism gene set; MD, meristem response and development gene set; PH, photoperiod pathway, circadian clock, and light signaling gene set; VA, vernalization and autonomous pathways gene set