PAUP* version 4.0 is a major upgrade and new release of the software package for inference of evolutionary trees, for use in Macintosh, Windows, UNIX/VMS, or DOS-based formats. The influence of high-speed computer analysis of molecular, morphological and/or behavioral data to infer phylogenetic relationships has expanded well beyond its central role in evolutionary biology, now encompassing applications in areas as diverse as conservation biology, ecology, and forensic studies. The success of previous versions of PAUP: Phylogenetic Analysis Using Parsimony has made it the most widely used software package for the inference of evolutionary trees. In addition, the PAUP manual has proven to be an essential guide, serving as a comprehensive introduction to phylogenetic analysis for beginning researchers, as well as an important reference for experts in the field. With the inclusion of maximum likelihood and distance methods in PAUP* 4.0, the new version represents a great improvement over its predecessors. In addition, the speed of the branch-and-bound algorithm has been enhanced and a number of new features have been added, from agreement subtrees to tests for combinability of data and permutation tests for nonrandomness of data structure. These, along with many other improvements, will make PAUP* 4.0 an even more indispensable tool in comparative biological analysis than were previous editions of the program and manual. PAUP* 4.0 and MacClade 3 use a common data file format (NEXUS), allowing easy interchange of data between the two programs.
