Figure 3. A) Phylogeny of coronaviruses (CoVs) in the RNA-dependent RNA polymerase gene (RdRp, 817-bp fragment) with root point dates derived from Bayesian inference under a relaxed lognormal molecular clock assumption with a codon-based substitution model (SRD06) and an assumption of expansion growth of the virus population. Estimated dates of diversification of CoV lineages at root points are shown in italics for the expansion growth population model and in regular type for the exponential growth model. Dates bc are identified with a suffix; dates ad are not. B) Bayesian phylogeny from the CoV group 1 root, using the nucleocapsid (N) gene. Highest posterior densities for all root points were >0.99, except where indicated.