MrBayes is a program for the Bayesian estimation of phylogeny. 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.
The program takes as input a character matrix in a NEXUS file format.
The output is several files with the parameters that were sampled by
the MCMC algorithm. MrBayes can summarize the information in these files
for the user. The program features include:
- A common command-line interface for Macintosh, Windows, and UNIX
operating systems;
- Extensive help available via the command line;
- Ability to analyze nucleotide, amino acid, restriction site, and
morphological data;
- Mixing of data types, such as molecular and morphological characters,
in a single analysis;
- A general method for assigning parameters across data partitions;
- An abundance of evolutionary models, including 4 X 4, doublet,
and codon models for nucleotide data and many of the standard
rate matrices for amino acid data;
- Estimation of positively selected sites in a fully hierarchical
Bayes framework;
- The ability to spread jobs over a cluster of computers using MPI
(for Macintosh and UNIX environments only).
The most recent version of the program, 3.1, is the first non-beta
release of MrBayes 3. Compared to previous beta versions, it includes numerous bug
fixes as well as several new features such as topology constraints,
inference of ancestral states and site rates, and simultaneous independent
runs with convergence diagnostics calculated on the fly.
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