Boxplot of Ka over Ks. Boxplot of Ka/Ks value for the four groups: N_F, A_F, N_S, and A_S (no AS gene families genes, AS gene families genes, no AS singletons, and AS singletons, respectively) across three different identity criteria (>10, >50, and >90). Overall, there is no significant difference observed for Ka over Ks values among singletons. For duplicated gene sets, the most similar gene families N_F (>90) and A_F (>90) have the top two highest Ka over Ks which imply a higher evolutionary rate. Conversely, those more anciently duplicated genes with AS, i.e. A_F (>10) and A_F (>50), have the lowest Ka over Ks values.