Systematics Section / ASPT
Kron, Kathleen A. .
Evolutionary relationships among major clades of Rhododendron (Ericoideae, Ericaceae).
RHODODENDRON (ca. 800 spp.) have been divided into several subgenera or sections based on morphological characteristics. This study addresses the evolutionary relationships among the four largest clades within Rhododendron: subgenera Rhododendron (lepidotes), Hymenanthes (elepidotes), Tsutsusi (evergreen azaleas) and section Pentanthera (azaleas). Each of these groups have been recognized by morphological characters (e.g., subgenus Rhododendron possess scales, subgenus Tsutsusi possess leaves and flowers within the same terminal bud). Previous studies have shown the subgenera Rhododendron (including section Vireya), Hymenanthes, and Tsutsusi are strongly supported as monophyletic. Subgenus Pentanthera is not monophyletic, but section Pentanthera is strongly supported as a clade. Although these groups are consistently supported as monophyletic in previous analyses, strong statistical support for relationships among them and the closely related Menziesia have been difficult to obtain. This study uses nucleotide sequence data from six regions (three chloroplast and three nuclear) to address the relationships of the traditional groups of Rhododendron and the position of Menziesia. Separate analyses of each partition resulted in poor resolution among the major clades but no conflict. Combined analyses result in excellent resolution with strong bootstrap support for Menziesia sister to Tsutsusi, sect. Pentanthera sister to Hymenanthes, and subgenus Rhododendron sister to the Pentanthera + Hymenanthes clade. The short branches that link these clades together suggest that early in the history of Rhodoreae a rapid diversification resulted in the ancestors to the easily recognized clades extant today. These clades have likely been maintained for some time with very recent radiations occurring in the Hymenanthes clade and in the tropical members of the Rhododendron clade.
Log in to add this item to your schedule
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
Date: Tuesday, August 1st, 2006
Time: 4:00 PM