Systematics Section / ASPT
Mayer, Michael , Davitt, Joseph .
Phylogeny and Biogeography of the Thelypodiine Alliance (Brassicaceae).
The term Thelypodiine alliance has been recently coined to circumscribe a group of new world mustards that includes tribe Thelypodieae (as circumscribed by Al-Shehbaz in 1973), all new world Sisymbrium species and its segregrates (tribe Sisymbrieae), Sibara (tribe Arabideae), and Pringlea (tribe Pringleae). This alliance exhibits a staggering array of floral diversity, unmatched by any other group of mustards. Despite this morphological variation, phylogenetic resolution within and among genera of the alliance has been difficult to achieve. We have previously reported that analyses of ITS and ndhF sequences reveal a basal position of Thelypodiopsis species, which suggests a Great Basin origin of the alliance. Ongoing analyses of these sequences including additional taxa are providing some further resolution, such as a major clade that includes several Thelypodium species of the southwest U.S. and adjacent Mexico, species of Guillenia (a segregate of Caulanthus) and all South American Sisymbrium species thusfar tested, as well as Pringlea antiscorbutica of the south Atlantic island of Kerguelen. This combination of taxa is rather unexpected from a morphological basis, but is cohesive geographically. Our new work has also clarified the relationships of many of the monotypic genera of the alliance. However, basal nodes in the alliance continue to garner low support, reaffirming earlier conclusions that this alliance must have radiated rapidly, probably in response to drying climates in the Neogene period.
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1 - University of San Diego, Department of Biology, 5998 Alcala Park, San Diego, California, 92110, USA
2 - University of San Diego, Department of Biology, 5998 Alcala Park, San Diego, California, 92110, USA
Presentation Type: Oral Paper
Date: Tuesday, August 16th, 2005
Time: 3:00 PM