Polyscias is the second largest genus in Araliaceae, with ~130 species, and is found throughout much of the old world tropics. Areas with high species diversity of Polyscias include New Caledonia, Australia, Malesia and Madagascar. The current broad definition of Polyscias includes all araliads with imparipinnate leaves, panicles of umbels, and articulated pedicels. However, recent molecular phylogenetic studies have shown that the genus is paraphyletic, including within it as many as nine different genera. Recent investigations have broadened the sampling of the Indian Ocean Basin (IOB) group of Polyscias and its presumed close relatives (Cuphocarpus and Gastonia) using nuclear (ITS) and chloroplast (trnLŠtrnF) markers to test the phylogenetic relationships within this large group. Results strongly support previous findings suggesting that the Indian Ocean group of Polyscias is paraphyletic, with close affinities to Malesian Polyscias, Gastonia, and the Hawaiian Tetraplasandra group. Maximum parsimony analyses further suggest that Gastonia is polyphyletic, and that the genus Cuphocarpus lies within the IOB group of Polyscias. In addition, preliminary evidence suggests that Cuphocarpus may not be monophyletic. Based on the molecular phylogenetic reconstruction, we propose six new subgroups within the IOB group of Polyscias (Northeast Malagasy Polyscias group, African-Comoro Polyscias group, P. tennantii group, P. myrsine group, P. baretiana group, and Mascarene Islands group), and describe morphological characters and geographic affinities shared by members of each group.

Key words: Araliaceae, Cuphocarpus, Gastonia, Indian Ocean basin, Madagascar, Polyscias