Systematics Section / ASPT
McMahon, Michelle .
Phylogeny and biogeography of dry tropical Dalea (Fabaceae: Papilionoideae: Amorpheae).
The legume clade Dalea + Marina comprise ~200 species whose species diversity is highest in the drier habitats of the Mexican Plateau and the Andes. Phylogenetic analysis for the clade using DNA sequence data indicates that at least two lineages invaded from North America to South America. Estimation of branch lengths indicates that these invasions occurred relatively recently. No evidence of migration from South America to North America has been found. The two lineages differ in their inferred age in the Andes and in the apparent speciation rate. The slightly older invasion resulted in geographically separated varieties of a widespread, primarily Mexican species, Dalea carthagenensis. The second invasion resulted in a radiation of ~19 species, the Coeruleae group, which appears to have radiated far more substantially in a shorter period of time. Structure within the Coeruleae group is limited by low levels of sequence variation but supports a general north-to-south migration pattern. The pattern seen in Dalea, i.e., recent migration from dry habitats in Mexico to the Andes without reverse migration followed by rapid speciation, parallels patterns seen in other groups such as the legume group Lupinus, lending support to the view of the Andes as a remarkable biodiversity hotspot for dry-tropical plants.
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1 - University of Arizona, Department of Plant Sciences and UA Herbarium, 1140 E. South Campus Dr., Tucson, Arizona, 85721, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 3/Hilton
Date: Wednesday, July 11th, 2007
Time: 4:45 PM