mrbayes binary package in Ubuntu Mantic amd64

 Bayesian inference of phylogeny is based upon a quantity called the posterior
 probability distribution of trees, which is the probability of a tree
 conditioned on the observations. The conditioning is accomplished using
 Bayes's theorem. The posterior probability distribution of trees is
 impossible to calculate analytically; instead, MrBayes uses a simulation
 technique called Markov chain Monte Carlo (or MCMC) to approximate the
 posterior probabilities of trees.

Source package