Systematics/Phytogeography / Taxonomie/ Section
Schuster, Tanja M. , Kron, Kathleen A. .
Preliminary Phylogenetic Relationships of Muehlenbeckia Meisn. (Polygonaceae).
Muehlenbeckia in the Polygonaceae comprises approximately 33 species, though the last revision by Brandbyge (1993) only recognizes 23 taxa. Most members of this group are twining vines, lianas or shrubs. Muehlenbeckiae are predominantly found in disturbed habitats and some are used as ornamentals. Muehlenbeckiaís distribution is amphipacific, with taxa occurring in Central and South America, Papua New Guinea, Australia and New Zealand. Morphologically, the genus is recognized via a combination of characteristic features such as, extrafloral (pit) nectaries on the petiole base, fimbriate or pennicilate stigmas and a persistent, baccate perianth. The ocreae, so characteristic for Polygonaceae, are often not persistent. Flowers may be unisexual and/or bisexual on an individual plant. Recently, it has been shown that Muehlenbeckia belongs in the strongly supported Polygonoideae rather than with Coccoloba P. Browne, Antigonon Endl. and Brunnichia Banks ex Gaertn., where it had been placed previously based on morphological characters. The latter taxa are members of a strongly supported Eriogonoideae. This is the first study of Muehlenbeckia that tests its monophyly and placement in Polygonaceae with molecular techniques. In order to examine the phylogenetic relationships of Muehlenbeckia, three chloroplast (rbcL, matK, ndhF) and one nuclear (ITS) marker were used for six Muehlenbeckia species and additional taxa in the Polygonoideae and Eriogonoideae. Parsimony analyses show that Muehlenbeckia includes Homalocladium platycladum (F.J. Muell) L.H. Bailey, which form a moderately supported clade. Homalocladium platycladum, formerly M. platyclados (F.J. Muell. Ex Hook.) Meisn., therefore renders Muehlenbeckia paraphyletic unless included in the latter. This result has consequences concerning the naming of Homalocladium and the interpretation of the biogeographical history of the investigated taxa.
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1 - Wake Forest University, Department of Biology, PO Box 7325, 226 Winston Hall, Winston-Salem, North Carolina, 27109-7325, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Room 1/Woodward
Date: Monday, July 28th, 2008
Time: 9:15 AM