Systematics Section / ASPT
Goodson, Barbara , Rehman, Sumaiyah , Santos-Guerra, Arnoldo , Jansen, Robert K. .
Molecular systematics and biogeography of Descurainia Webb & Berthel. (Brassicaceae) based on nuclear ITS and non-coding chloroplast DNA.
Descurainia Webb & Berthel. (Brassicaceae) comprises approximately 45 species distributed throughout temperate areas of the Old and New World. The genus, which is noted for its taxonomic complexity, is most diverse in western North America and western South America, with a smaller center of distribution in the Canary Islands and three additional Old World species. A molecular-based phylogeny for Descurainia has been constructed using DNA sequences obtained for nuclear ITS and non-coding chloroplast regions. ITS and trnL data support the inclusion of Descurainia in the recently-designated tribe Descurainieae. The placement of Hugueninia within Descurainia is strongly confirmed, and the possible expansion of Descurainia to include Robeschia and Ianhedgea is suggested. Phylogenies based on ITS, chloroplast rps16 intron, and chloroplast trnD-trnE, trnE-trnT, trnC-ycf6, ycf6-psbM, psbZ-trnfM, and ndhF-rpl32 intergenic spacer regions suggest a recent origin in the Irano-Turanian region of the Old World for Descurainia, with subsequent diversification during the late Pliocene or early Pleistocene into Europe and into the New World. Species in the Canary Islands are monophyletic, implying a single colonization event into the islands, and are most closely related to European Hugueninia. The phylogeny recovered from combined ITS and chloroplast data suggests that multiple independent dispersals have taken place between North and South America. Substantial incongruence between ITS and chloroplast phylogenies, as well as the presence of polymorphic ITS sequences, point to a complex evolutionary history involving extensive gene flow for North American Descurainia.
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1 - University of Texas at Austin, Section of Integrative Biology, 1 University Station, #A6700, Austin, TX, 78712, USA
2 - Jardín de Aclimatación de La Orotava, Puerto de la Cruz, Canary Islands, Tenerife, Spain
Presentation Type: Oral Paper:Papers for Sections
Location: Boulevard C/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:45 AM