Redden, Karen M. .
Systematics, Biogeography and Diversity of the genus Dicymbe (Leguminosae: Caesalpinioideae).
The Leguminosae (650 genera/~18,000 species) is the third largest family of flowering plants and the second most economically important family. Among the three subfamilies, understanding relationships among the genera of Caesalpinioideae is critical for establishing a family-level evolutionary framework as they constitute the early branches of legume phylogeny. Of further interest, Caesalpinioideae also contain many of the most morphologically diverse within the family; these are little studied relative to other subfamilies. Tribe Detarieae contains many of these genera that are rarely collected large rainforest trees. Like other members of Detarieae, Dicymbe (20 spp.) occurs only on the Guiana Shield, one of the oldest geological formations in South America. Some species of Dicymbe have ectomycorrhizal associations, can form monodominant stands, and exhibit mass synchronized flowering/fruiting events. The genus contains both widely distributed taxa and narrow endemics found only on the tepuis. The biogeographic interest of Dicymbe is enhanced as its sister group, Polystemonanthus, is restricted to West Africa. No comprehensive monographic revision has been done for Dicymbe, and species boundaries remain unclear. This study examines the distributional disjunctions between the species of Dicymbe, as well as with Polystemonanthus, in a phylogenetic context. Using a total evidence approach combining morphological and sequence data (plastid and low-copy nuclear gene regions), radiation patterns of these Shield endemics are explored and compared with those of other species in the closely related Brownea clade of South America. Likewise, broader biogeographic patterns are compared between Shield and West African species. Furthermore, morphological characters are explored and reevaluated for species identification.
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1 - Smithsonian Institution - National Museum of Natural History, Department of Botany, P.O. Box 37012, Washington, DC, 20013, United States
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Maybird/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 8:30 AM