Systematics Section / ASPT
Fishbein, Mark , Lynch, Steven P. , Chuba, David , Weitemier, Kevin , Ellison, Christopher , Goyder, David J. , Chase, Mark W. , Mason-Gamer, Roberta .
Phylogeny and Biogeography of North American Asclepias (Apocynaceae).
Phylogenetic study of milkweeds (Asclepias sensu lato, Apocynaceae) has lagged behind extensive study of the reproductive and chemical ecology of this well known genus. Previous study has revealed that, in the broadest sense, nearly all Asclepias species fall into one of two sister clades: an American clade of c. 135 spp. and an African clade of c. 250 spp. Current practice restricts the circumscription of Asclepias to the American clade. In a previous study, we reported moderate phylogenetic resolution of several major clades of American species, although relationships among and within these clades were not well resolved with three cpDNA loci (rpl16 intron, trnC-rpoB spacer, trnS-G spacer/trnG intron). Here we use a subsampling approach, two additional cpDNA loci (trnD-trnT spacers and rpl32-trnL spacer), and three nuclear loci (LFY, G3PDH, and PgiC) to resolve relationships among major clades and test biogeographic hypotheses. Phylogenetic estimates were obtained using standard parsimony and Bayesian approaches and alternative hypotheses were tested using likelihood-ratio tests. The biogeographic history of the group was explored using Dispersal-Vicariance Analysis and rate-heterogeneous dating of nodes. Overall, the diversification of Asclepias in the Americas has involved 1) a single colonization from North to South America, 2) radiations into Mexican highlands from temperate North American lineages, and 3) post-Pleistocene expansion and diversification in temperate grasslands and forests.
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1 - Portland State University, Biology Department, Po Box 751, Portland, Oregon, 97207-0751, USA
2 - Louisiana State University-Shreveport, Biological Sciences, One University Place, Shreveport, Louisiana, 71115, USA
3 - Portland State University, Biology, P.O. Box 751, Portland, Oregon, 97207-0751, USA
4 - University of California, Plant and Microbial Ecology, Berkeley, California, 94720, USA
5 - Royal Botanic Garden, Kew, Herbarium, Richmond, Surrey, TW9 3AB, United Kingdom
6 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kingdom
7 - University of Illinois Chicago, Department of Biological Sciences, M/C 066, 845 W Taylor Street, Chicago, Illinois, 60607, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 2:15 PM