Systematics Section / ASPT
Plunkett, GM , Lowry II, Porter P. , Vu, Ninh V. .
Paraphyly, Polyphyly, and Geography in Polyscias sensu lato (Araliaceae): Examples from the Indian Ocean Basin Clade.
Molecular evidence based on ITS sequence data suggests that the genus Polyscias (Araliaceae) is paraphyletic. The most exclusive clade that unites all species of Polyscias also includes Tetraplasandra, Reynoldsia, Munroidendron, Arthrophyllum, Gastonia, and Cuphocarpus. Within a broadly expanded "Polyscias sensu lato" clade that includes all seven genera, preliminary studies suggested that the taxa native to the Indian Ocean Basin (IOB) are monophyletic. Expanding both the number of molecular markers (trnL-trnF plus ITS) and species sampling, we have identified a monophyletic (albeit weakly supported) clade of IOB taxa that is sister to a clade of Malesian and Pacific species. Included within the IOB clade are some but not all representatives of Gastonia, which is thus polyphyletic within Polyscias sensu lato. All samples of the Malagasy endemic Cuphocarpus fall within the IOB clade, but in two separate subclades, rendering another genus polyphyletic. These results add to a growing body of evidence that the morphological characters traditionally used to define genera in Araliaceae (especially carpel number and pedicel articulation) have been applied too simplistically and rigidly. Geographically, all major subclades among IOB Polyscias include species from Madagascar, suggesting that the group originated on this continental island. A single radiation (probably via dispersal) can account for the clade restricted to the Mascarene Islands, but there appear to have been at least two separate dispersals each from Madagascar to continental Africa and to the Comoro Islands. Data are not yet available for species from the Seychelles, but recent collections in these islands will allow us to explore their relationship to the broader IOB clade.
1 - Virginia Commonwealth University, Department of Biology, P.O. Box 842012, Richmond, Virginia, 23284-2012, USA
2 - Missouri Botanical Garden, PO Box 299, St. Louis, Missouri, 63166-0299, USA
Indian Ocean Basin.
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 12:00 PM