A LIKELIHOOD-RATIO TEST OF MONOPHYLY

Many phylogenetic analyses are inspired by or depend upon the monophyl y of a group specified a priori. Also, many evolutionary problems for which phylogenies are useful do not require every detail of the phylog eny to be estimated correctly but depend upon the monophyly (or lack t hereof) of a particular group. We propose a likelihood-ratio test that compares whether the best trees estimated with and without the constr aint of monophyly are significantly different. Simulation suggests tha t the test is conservative when the null hypothesis (a particular spec ified constraint) is correct. We applied the likelihood-ratio test of monophyly to the question of the relationship of the presumed-extinct marsupial wolf (Thylacinus). Specifically we examined the null hypothe ses that (1) the marsupial wolf does not form a monophyletic group wit h dasyurids and (2) the marsupial wolf is a basal member of the Austra lian radiation of mammals. Both hypotheses were rejected using the lik elihood-ratio test of monophyly.