Systematics Section / ASPT
Kron, Kathleen A. , Bush, Catherine , Lamb-Frye, Ann S. .
Systematics of Rhododendron subgenus Rhododendron based on chloroplast nucleotide sequence data.
One of the most diverse groups within the genus Rhododendron is the lepidote or scaly rhododendrons that occur in temperate and tropical regions of Asia, and in North America and Europe. Most of the nearly 400 species in R. subgenus Rhododendron (lepidotes) occur in the Asian tropics and have been classified as section Vireya. The remaining species are temperate or boreal plants with a high concentration of species in the Himalaya. Phylogenetic relationships among representatives of R. subg. Rhododendron are investigated using nucleotide sequence data from two chloroplast genes, matK, ndhF, and intergenic spacers within the trnS-trnG-trnG region. Taxon sampling includes species from three of the three recognized sections (Rhododendron, Pogonanthum, Vireya). Within section Rhododendron, one to five species from 17 of the 27 recognized subsections were represented and these taxa also cover the geographic range of the section. Six subsections are recognized within the Vireya group and all of these groups are represented by at least one species. In subsections with numerous species proportionally more species were sampled. Outgroup taxa include representatives from section Pentanthera and subgenera Tsutsusi and Hymenanthes. The trees were rooted with R. molle. Combined parsimony analysis of data from all three genes/regions indicate two large clades within subgenus Rhododendron. These clades have moderate to strong bootstrap support and are also strongly supported as sister groups. None of the currently recognized subsections for which two or more species were sampled are monophyletic. Informal groups recognized by previous workers, based on seed, style, and leaf epidermal characters are also not supported in this analysis. The Vireya rhododendrons are not monophyletic with R. lapponicum strongly supported as sister to nine of the 12 species sampled. Two other Vireya representatives are placed within a clade containing representatives from subsections Afghanica, Campylocarpa, Glauca, Micrantha, and Tephropepla.
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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: 3:30 PM