Systematics Section / ASPT
Plunkett, Gregory M. , Lowry, Porter P. II .
Evolution and Biogeography in Melanesian Schefflera (Araliaceae): a Preliminary Assessment Based on ITS and ETS Sequence Data.
The genus Schefflera represents one of the most significant challenges to the systematics of Araliaceae. It is the family’s largest genus (with over 900 species), but recent evidence has demonstrated its significant polyphyly, with five unrelated clades of Schefflera spread throughout the phylogenetic tree of the family. One of these clades, informally called “Melanesian Schefflera” (with c. 50 species), is distributed on the islands of the southwestern Pacific Ocean (ranging from Fiji to New Guinea), with a center of diversity in New Caledonia. Morphological data suggest that this clade may be divided into five subgroups (four of which range broadly throughout Melanesia). We used nuclear sequence data from two non-coding regions (ITS and ETS) to examine phylogenetic and biogeographic relationships in this clade. Preliminary results confirm the monophyly of Melanesian Schefflera and three of its subgroups (“Plerandra,” “Gabriellae,” and “Canacoschefflera”). A fourth subgroup, “Dizygotheca,” is morphologically and cytologically very distinctive, but appears to be polyphyletic in the cladogram based on nuclear markers; additional data must be collected to test this surprising result. Only one species from the small “Dictyophlebes” subgroup could be sampled, but this appears to be closely related to “Plerandra.” Biogeographically, Melanesian Schefflera appears to have originated in New Caledonia. From this island, there were multiple dispersals to other areas of Melanesia, including Vanuatu (in the “Dizygotheca” subgroup), at least two independent dispersals to Fiji (in “Gabriellae” and in the “Plerandra”+”Dictyophlebes” clade), plus one dispersal from Fiji to New Guinea (in “Plerandra”). In general, these results parallel the findings in other clades of Araliaceae from the Pacific, including Polyscias and Meryta, suggesting a common pattern of dispersal among plants of the insular southwest Pacific.
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1 - Virginia Commonwealth University, Department of Biology, P.O. Box 842012, Richmond, Virginia, 23284
2 - Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri, 63166
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Monday, July 9th, 2007
Time: 1:00 PM