Codon Adaptation Index of the Lost genes and the Retained genes in the marine <i>Synechococcus</i> genomes at different stages in <i>Prochlorococcus</i> evolution.

Time: LCA is the root of the tree, which is also the last common ancestor of Prochlorococcus and Synechococcus; Branch labels are same as those in Figure 3. P-value: P-values of Student's t tests. The null hypothesis is: the Lost group has the same mean as the Retained group.