Systematics Section / ASPT
Lamb Frye, Ann S. , Kron, Kathleen A. .
Evolutionary relationships in Rhododendron subgenus Hymenanthes, as indicated by analysis of chloroplast regions, matK, ndhF and trnS-trnG-trnG.
The elepidote evergreen rhododendrons (Rhododendron subgenus Hymenanthes) include approximately 225 species distributed in temperate areas of Asia, Europe and North America. Many species are of horticultural importance due to the presence of large showy flowers. Subgenus Hymenanthes has been divided into 24 subsections based on overall similarity of floral and indumentum characters. These subsections have been arranged into three informal groups based on generalized aspects of the morphology. Sequence data from three chloroplast regions (matK, ndhF and trnS-trnG-trnG) were used to investigate the evolutionary relationships within Rhododendron subgenus Hymenanthes and to test the monophyly of previously recognized morphological groups. Taxa sampled for the analysis included 1-5 species from each of the 24 subsections of Hymenanthes and representatives from subgenera Tsutsusi, Rhododendron and Pentanthera. Rhododendron molle was designated as an outgroup in all analyses, which were conducted using maximum parsimony. Sequence variation among the species was very low in the matK and ndhF genes. The trnS-trnG-trnG intergenic spacer region yielded more variable sequences among species. Parsimony results indicated that most of the previously recognized subsections, for which more than one species was sampled, are not monophyletic. The informal morphological groups also did not receive bootstrap support. The concentration of species diversity of elepidote rhododendrons in the Himalaya, a relatively new geologic region, may represent a rapid and/or a recent speciation event. The chloroplast data would support this due to the relatively high consistency and retention indices, despite the lack of resolution of relationships.
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1 - Wake Forest University, Department of Biology, P.O. Box 7325, Winston-Salem, North Carolina, 27109, USA
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 4:00 PM