Plunkett, Gregory , Nicolas, Antoine N. , Lowry, Porter P. II , Fiaschi, Pedro , Frodin, David G. .
Phylogenetic relationships among and within the Asian and Neotropical groups of Schefflera (Araliaceae) based on six molecular markers.
Schefflera is the largest and most complex genus of Araliaceae, with ~600 described species (and possibly 400+ additional species awaiting description). However, recent studies indicate that Schefflera forms five geographically-centered clades spread across the major lineages of the family. Despite this polyphyly, a thorough revision and division of the genus awaits more complete sampling across all five clades. Significant progress has been made in three smaller clades, but the two largest groups, centered in Asia and the Neotropics (300+ spp. each), remain poorly understood. To advance our knowledge of these groups, we assembled 200+ representatives from these two clades, plus samples from all other genera in the “Asian Palmate clade” of Araliaceae. DNA sequences were obtained from six molecular markers, including two nuclear (ITS, ETS) and four plastid spacers (rpl32-trnL, trnF-rpl32, trnK-rpl16, psbA-trnH). Results were compared to an informal system of classification based on morphology. Both nuclear and plastid data confirm the monophyly of both groups, but suggest that they are more distantly related than previously thought, despite a series of remarkable convergences. In the Neotropical clade, six major subclades can be recognized, five corresponding closely to morphological groupings (Sciodaphyllum, Attenuatae, Didymopanax, Cephalopanax, and Crepinella). The sixth group (Cotylanthes) falls within the broader Sciodaphyllum subclade, and molecular data provide evidence for an additional subclade uniting the Caribbean S. tremula and S. gleasonii. Within Asian Schefflera, there are four major subclades. Three correspond closely to currently recognized informal groups (Agalma, Heptaphyllum, and Hypoleucoi), while the fourth and largest subclade includes representatives sampled from all remaining groups (formerly assigned to Asian Sciodaphyllum). These include Brassaia, Tupidanthus + Paratropia, Heptapleurum + Farinosae, and Papuoschefflera. Given our sample set (representing six of the eight morphological groupings from Asia and all six of the Neotropical groups), it appears that all major clades of Schefflera sensu lato have now been identified. Future studies should focus on more intensive sampling within each of these major clades.
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1 - New York Botanical Garden, Cullman Program for Molecular Systematics, 2900 Southern Blvd., Bronx, NY, 10458, US
2 - New York Botanical Garden, Institute of Systematic Botany, 2900 Southern Blvd., Bronx, NY, 10458, US
3 - Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri, 63166
4 - Virginia Commonwealth University, Department of Biology, P.O. Box 842012, Richmond, Virginia, 23284
5 - Royal Botanic Gardens, Kew, Herbarium, Richmond, Surrey, TW9 3AB, England
Presentation Type: Oral Paper:Papers for Sections
Location: 556B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 1:15 PM