What is PACT really?

Abstract

"Phylogenetic Analysis for Comparing Trees" (PACT) has been presented as a "new algorithm" for the study of biogeography and coevolution. However, an exploration of this algorithm revealed some important problems missed in the original description. First, PACT is not new, rather it is an extension of Tree Mapping under Maximum Codivergence (TM-MC). Second, as was described, PACT lacks an optimality criterion, and like secondary BPA, it does not offer a solution for handling incongruent elements. We found that PACT and TM-MC differ only in the way the final answer is presented, and in the absence of an explicit algorithm of historical reconstruction under PACT. Given the equivalence between TM-MC and PACT in their aims and assumptions, the criticism to TM-MC as "orthogenetic" is not well founded. © The Willi Hennig Society 2008.