The Tetraplasandra group incorporates four genera, Tetraplasandra, Munroidendon, Reynoldsia, and Gastonia, that are distributed from East Africa, through the islands of the Indian Ocean and Malesia, to the Solomon Islands, Samoa, Tahiti, the Marquesas, and the Hawaiian archipelago (Philipson, 1970, Lowry, 1990). For such a small group (approx. 23 species), there is remarkable diversity in floral morphology. Inflorescence architecture fluctuates between paniculate umbellate and compound umbellate, ovary position ranges from inferior to fully superior, and carpel and stamen numbers vary greatly. A phylogeny based on nuclear ribosomal Internal Transcribed Spacer regions (ITS 1 and 2), the non-transcribed spacer region of nuclear ribosomal 5S (52-NTS), and morphology strongly supports the monophyly of the Hawaiian taxa Tetraplasandra, Munroidendron, and Reynoldsia sandwicensis and places the extra-Hawaiian Reynoldsia species that are distributed in Samoa and French Polynesia as sister taxa. Both Reynoldsia and Gastonia are paraphyletic. The evolution of floral morphology and relationships in the Tetraplasandra group will be discussed.

Key words: 5S-NTS, Gastonia, ITS, Munroidendron, Reynoldsia, Tetraplasandra