Model comparisons for analyses relaxing the assumption of autocorrelation of rates across the tree. Harmonic mean model likelihoods were calculated from post-burnin MCMC samples generated in BEAST. For these model comparisons, the topology was fixed as TConsensus. The strict clock model serves as a base comparison. The tree TFlexible refers to analyses where topology is not fixed. Covariance indicates the degree of substitution rate autocorrelation between ancestor and descendent branches. 95% HPDs are given in parentheses.