Fig. 2.

The new method schematic. In step 1 coalescent trees for the aligned DNA sequences are sampled from an MCMC simulation using an importance sampling distribution of trees that is free of a demographic model of interest. In step 2, the set of sampled coalescent trees is used for the approximation of the joint posterior density under a demographic model of interest. Optimization of the joint posterior density provides an estimate of model parameters. The same set of trees from step 1 can be used repeatedly to study different demographic models.