Strength of codon adaptation across lineages.

<p>A phylogeny of plastids with the strength of codon adaptation indicated for different lineages. Strength of selection is based on the S_pca measure described in the text and given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0154306#pone.0154306.s001" target="_blank">S1 Table</a>. An average value for the plastids within a given lineage greater than 1 is considered strong adaptation and an average value less than -1 is considered weak adaptation. A dashed line indicates variation within the genomes of that lineage. The primary endosymbiont is indicated as are the two proposed secondary events, one from green plant ancestors to the Euglenoids and another from the red algae ancestors to the lineage leading to extant Cryptophytes, Alveolates, Stramenopiles and Haptophytes (see text). Branches preceding the endosymbiosis are shaded black and indicate a lack of a plastid. The phylogeny overall is based on the general relationships from different sources [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0154306#pone.0154306.ref013" target="_blank">13</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0154306#pone.0154306.ref014" target="_blank">14</a>].