Species diversity
The earliest ribosomal gene sequence data indicated that "Symbiodinium" had lineages whose genetic divergence was similar to that seen in other dinoflagellates from different genera, families, and even orders. This large phylogenetic disparity among clades A, B, C, etc. was confirmed by analyses of the sequences of the mitochondrial gene coding for cytochrome c oxidase subunit I (CO1) among Dinophyceae. Most of these clade groupings comprise numerous reproductively isolated, genetically distinct lineages (see ‘Species diversity’), exhibiting different ecological and biogeographic distributions (see ‘Geographic distributions and patterns of ‘diversity’).