Figure 1.

(a) A cyanobacterium breaking up the red/green lineage provides a refutation of monophyly. (b) The hypothesis preferred under Ockham's razor for explaining the origins of characters specific to red and green lineages, i.e. a single endosymbiosis, when no cyanobacteria have been sampled that (a) break up the red/green lineage. R and G indicate the origin of characters specific for the red and green lineages; the star indicates endosymbiosis.