Figure 4. Maximum likelihood phylogeny of concatenated leuC and leuD genes.

Numbers at nodes indicate RAxML rapid boostrap (left) and PhyML SH-aLRT supports (right), and nodes with full support are indicated by black dots. Nucleus-encoded plastid-targeted genes are boxed in green and major lineages labelled to the right. Gracilaria sequences are shown in white text on black: G. changii has canonical nucleus-encoded leuC and leuD genes but G. tenuistipitata has a plastid-encoded operon that appears to have been derived by recent horizontal gene transfer from a proteobacterial source. Phylogenies of leuC and leuD are largely congruent, and can be found in Figure S2. Black “O” after species name indicates that leuC/D operon is present, red “O” indicates it is intervened by one (Ch. flavus) or two short ORFs (S. termitidis).