Molecular phylogeny and biogeography of Melaleuca, Callistemon and relatedgenera (Myrtaceae)

To resolve the relationships of taxa within the Beaufortia suballiance (Myr taceae), 72 ingroup taxa were analysed by parsimony methods and nrDNA seque nce data from the 5S and ITS-1 ribosomal DNA spacer regions. Although basal nodes in the consensus tree (combined data set) are not supp orted by bootstrap or jackknife values, a number of clades are well support ed, showing that Melaleuca is polyphyletic. Monophyletic groups include: en demic species of Melaleuca from New Caledonia (including species of Callist emon recently transferred to Melaleuca); the tropical Melaleuca leucadendra group; Australian species of Callistemon, which relate to species of Melal euca predominantly from the South-East; and a group of south-western and ea stern Australian melaleucas that relate to a clade of three south-western g enera, Eremaea, Conothamnus and Phymatocarpus. Calothamnus, Regelia and Bea ufortia may also relate to this latter group. Lamarchea is possibly related to northern melaleucas. The results have implications for generic revision s of the large genus Melaleuca. Biogeographic subtree analysis, based only on supported nodes of the taxon cladogram, showed New Caledonia, New Guinea, Eastern Queensland and the Nor thern Desert unresolved at the base of the area cladogram. The position of some of these areas is likely to be artifactual, but New Caledonia is inter preted as in the correct position. At a higher node, the monsoonal northern areas of Australia (Kimberley, Arnhem and Cape York), Atherton, the Pilbar a and Western Desert relate to the southern regions, which form a group. Th e South-West of Australia is related to Eyre and Adelaide (designated area 'South') and Tasmania is related to the South-East and MacPherson-Macleay. The vicariance between northern and southern regions in Australia possibly relates to an early major climatic change (from the Early Tertiary). The bi ogeographic analysis helped illuminate taxon relationships.