Farruggia, Frank T. , Wojciechowski, Martin F. .
Evolutionary relationships of Sesbania Scop. (Leguminosae) and patterns of biogeography and morphological character evolution.
The legume genus Sesbania Scop. (tribe Sesbanieae) is comprised of approximately 78 species distributed throughout tropical and subtropical wetlands, riparian, and coastal habitats. Many features of Sesbania, such as pod morphologies, biogeography and ecological predilection, make it unique among papilionoids and especially compared to its related tribes Loteae and Robinieae. This study investigates the phylogenetic relationships among Sesbania species and resolves the relationships between the Robinieae, Loteae, and Sesbania. Phylogenies produced using three nuclear regions (TRPT, nfr5 and nrDNA ITS) along with the chloroplast regions trnK-matK and trnG-trnS indicate that Sesbania is more closely related to Loteae than Robinieae, as was previously hypothesized from analyses of matK data alone. Our results resolve two principal clades within Sesbania, which support the traditional classifications based on pod morphologies, and confirm that New World sections Daubentonia, Daubentoniopsis and Glottidium are monophyletic and comprise the sister group to a clade represented by section Sesbania, in which sections Agati and Pterosesbania are nested. Phylogenies based on analyses of TRPT and nrDNA ITS were also used to investigate biogeographic pattern and morphological character evolution. The phylogenetic results are consistent with an initial radiation of Sesbania from the New World (primarily North America) to Africa, followed by long-distance dispersal that resulted in the pantropical distribution of members of the section Sesbania clade. Morphological characteristics, such as seed number, size and shape, as well as fruit and perianth features, are useful synapomorphies for delimiting the principal subclades within Sesbania. The results of this study provide the data for Sesbania to be utilized as a model system to test nodulation processes and long-distance dispersal mechanisms.
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1 - Arizona State University, School of Life Sciences, P.O. Box 874501, Tempe, Arizona, 85287-4501, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Maybird/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 8:45 AM