A previous analysis of two chloroplast gene regions, rbcL and the rps16 intron, showed a clear phylogenetic pattern in Gunnera. However, these regions were not informative enough to completely resolve the phylogeny. In this study the nuclear ITS region was sequenced for 24 specimens representing 22 species of Gunnera. 223 characters out of 819 were informative and supported the same monophyletic groups as the chloroplast gene regions. Because of its greater information content, the ITS region identified additional well-supported clades. In an analysis based on the three gene regions together, 272 characters out of 3154 were informative. The results show that the South American annual, G. herteri is sister to all other species. The African G. perpensa is well-supported as sister to the remaining species, which form two well-defined clades, one with the Malayan G. macrophylla as sister to subgenus Milligania from New Zealand and Tasmania. In the other clade, the South American subgenus Misandra is sister group to subgenus Panke from South America and Hawaii. Within Panke the two Hawaiian species form a sister group to the American species. The morphological classification of Schindler, together with some biogeographical and morphological features, is discussed.
Communicating Editor: Paul Wilson