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Systematics Section / ASPT

Farruggia, F. T. [1], Delgado-Salinas, A. [2], Lavin, Matt [3], Wojciechowski, Martin F. [1].

Molecular phylogenetic analysis of the pantropical legume genus Sesbania.

The economically important genus Sesbania Adanson (Fabaceae) includes approximately 60 species of trees, shrubs, and perennial or annual herbs that are widely distributed in riparian and wetland habitats in tropical and subtropical regions of the world. The few taxonomic studies have consistently divided the genus into four to five infrageneric groups based almost entirely on pod morphology. Using sequences of the matK gene and nuclear rDNA ITS region, we have initiated a comprehensive analysis to resolve systematic and biogeographic relationships within Sesbania and among its closest papilionoid relatives, Loteae s. l. and Robinieae. Phylogenetic analysis of 52 matK sequences (including 10 species of Sesbania) shows strong support for monophyly of the robinioids, Loteae s. l., and Sesbania, although weak support for the relationships among these three lineages. Within Sesbania, three strongly supported clades are resolved, which correspond to sect. Glottidium, Daubentonia, and Sesbania. Phylogenetic analysis of nrDNA ITS sequences from 21 species of Sesbania, including sequences from Robinieae and Loteae s.l., also resolve the same three well supported principle lineages within Sesbania, consistent with the matK results. Notably, the results show sect. Daubentoniopsis, represented by S. longifolia, derived from within Daubentonia. Similarly, the monotypic sections Agati and Pterosesbania are resolved as nested within the largest sect. Sesbania. The position of S. grandiflora (sect. Agati) in this latter clade is expected, given that it has been treated in sect. Sesbania because of its shared linear pod morphology. However, the position of S. tetraptera (sect. Pterosesbania), a species restricted to Africa, within sect. Sesbania is unexpected given it possesses winged pods similar to members of sect. Daubentonia. The nrDNA ITS data suggests that biogeography is tracking phylogeny as well as or more so than pod morphology. The Daubentonia-Glottidium clade is essentially New World, whereas the sect. Sesbania clade is primarily Old World.

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1 - Arizona State University, School of Life Sciences, Asu, Main Campus, Po Box 874501, Tempe, Arizona, 85287-4501, USA
2 - Instituto de Biologia, UNAM, Departamento de Botanica, Mexico, D.F., , Mexico
3 - Montana State University, Department of Plant Sciences, Bozeman, Montana, 59717, USA

molecular systematics.

Presentation Type: Oral Paper
Session: 44-8
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 10:15 AM
Abstract ID:221

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