Summary of gene loss and gene gain events across the phylogenetic tree.

<p>Ancestral genome contents were reconstructed based on the phylogenetic tree in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088837#pone-0088837-g001" target="_blank">Figure 1</a> by maximum parsimony. Gene loss and gain events are summarized on the branches leading to the major clades of <i>Prochlorococcus</i>. The number in black is gene gain and the number in red is gene loss.