The origin and diversification of cyanobacteria as inferred from geologic time.
The phylogenetic tree was estimated based on 135 proteins and two ribosomal RNAs (SSU and LSU) from 131 taxa implementing Maximum Likelihood in RAxML GUI v.1.161. Bayesian relaxed molecular clock analyses were carried out in MCMCtree31. For the tree shown age estimates were estimated under the independent rates model33 for the RNA data set. Four calibrations (brown circles) were used2,67,68,69 for the tree shown and were treated as soft bounds. The root of the tree was set with a maximum age of 2,700 Myr63 and a minimum age of 2,320 Myr2. Numbered nodes 1–10 indicate divergence times for clades and key evolutionary events in the evolution of cyanobacteria including: the first origin of filamentous cells, ancestors of the Microcyanobacteria and Macrocyanobacteria, unicellular N-fixers and the marine Synechococcus and Prochlorococcus clades. Age estimates are given in Table 1, which includes the corresponding values for the posterior 95% confidence intervals.