Paraphyly and polyphyly in Polyscias sensu lato: molecular evidence and the case for recircumscribing the "pinnate genera" of Araliaceae
Plunkett, Gregory M.; Lowry, Porter P.
Seven Paleotropical genera of Araliaceae have imparipinnate leaves and belong to the single large "Polyscias sensu lato" clade. Current generic circumscriptions, however, fail to reflect the evolutionary history of the group. Building on earlier results, the present study employs an enhanced set of samples and a third molecular marker (nuclear ETS, in addition to nuclear ITS and the plastid trnL-trnF) to examine phylogenetic relationships in Polyscias sensu lato. Results confirm that Polyscias is paraphyletic with regard to the remaining six genera, three of which (Gastonia, Cuphocarpus, and Reynoldsia) are themselves polyphyletic. Of the three remaining genera, Tetraplasandra and Munroidendron are most closely related to Reynoldsia and thence to a set of Malesian species currently assigned to Polyscias and Gastonia, while Arthrophyllum belongs to a distinct clade of Polyscias species from Malesia, Australia, and the SW Pacific. Several formally recognized infra-generic groups within Polyscias are also non-monophyletic, including sections Eupteron and Kissodendron, while the single species of section Gelibia is best placed in the informally recognized section Tieghemopanax. The small type section (sect. Polyscias, with 13 species) is monophyletic, but restricting the generic concept to this clade presents a series of taxonomic and pragmatic difficulties.