Phylogeny of Melaleuca, Callistemon, and Related Genera of the Beaufortia Suballiance (Myrtaceae) Based on 5S and ITS-1 Spacer Regions of nrDNA.

A phylogenetic analysis of genera within the informal suballiance Beaufortia (family Myrtaceae), largely endemic to Australia and New Caledonia, is presented based on separate and combined data sets for 5S and ITS-1 spacer regions of nuclear ribosomal DNA. The two sets were not in conflict but the 5S data set was more informative. Data were analysed using conventional parsimony, jackknife parsimony, and three-item parsimony analyses. Three-item analysis gave more resolved trees than conventional parsimony analysis. The Beaufortia suballiance includes two major clades, with all Australian representatives of Callistemon (shown to be monophyletic) and most Australian representatives of Melaleuca forming one of these. The sister clade comprises a well-defined group of endemic New Caledonian taxa (classified as Callistemon and Melaleuca), some Australian species of Melaleuca, a clade including the Western Australia/Northern Territory genera Beaufortia, Lamarchea, and Regelia, and a clade including the south-west Western Australian genera Calothamnus, Eremaea, Conothamnus, and Phymatocarpus. All molecular analyses sup port the monophyly of Conothamnus and of Regelia, genera for which a number of species were included. Three-item analysis of the combined data set supports the monophyly of Beaufortia. The findings have implications for both taxonomy and biogeography.