Fig. 4 in A Systematist's Guide to Estimating Bayesian Phylogenies From Morphological Data

Fig. 4. Flowchart of the MCMC algorithm. In the MCMC algorithm, initial conditions are proposed and evaluated for likelihood.Then, the tree and/or other model parameters are changed.The likelihood of these new values is then evaluated. If they represent an improvement over the old ones, they are used to seed the next MCMC step. If not, they are rejected.