Phylogenetic Relationships amongPolyscias(Araliaceae) and Close Relatives from the Western Indian Ocean Basin

Abstract

As currently circumscribed, Polyscias is the second largest genus in Araliaceae, with ca. 150 species, and is found throughout much of the Old World tropics. Recent studies have shown that the genus is paraphyletic, including as many as eight additional genera in a broad “Polyscias s.l.” clade. This study focuses on relationships among the species of Polyscias native to the western Indian Ocean basin (IOB), which form one of the major subclades of Polyscias s.l. By expanding the sample of IOB taxa by a factor of four and combining data from both nuclear (ITS) and chloroplast (trnL‐trnF) markers, we have confirmed the close relationship of the IOB species to the Malesian members of Polyscias and Gastonia and aslo to the Pacific “Tetraplasandra group” (Tetraplasandra, Reynoldsia, and Munroidendron). Within the IOB clade, Polyscias is paraphyletic with regard to both Cuphocarpus and the remaining samples of Gastonia. Moreover, both Cuphocarpus and Gastonia are themselves polyphyletic. On the basis of the molecular phylogenetic reconstruction, we propose eight subgroups within the IOB clade, each of which is geographically coherent, and we describe morphological characters shared by members of each group. To strengthen our earlier proposals for generic circumscriptions and to assess Polyscias and its close relatives from beyond the IOB region, future studies should explore the remaining groups within Polyscias s.l. (e.g., the “Arthrophyllum group” and “section Polyscias group”), with a special emphasis on species from Malesia.