Recent Topics Posters
Ellison, Chris , Fishbein, Mark , Lynch, Steven P. , Mason-Gamer, Roberta .
Phylogenetic Relationships of Asclepias series Incarnatae (Apocynaceae) and the Origin of South American Asclepias.
ASCLEPIAS series Incarnatae (Apocynaceae) was erected by Woodson (1954, Ann. Mo. Bot. Gard. 41:1-211) to include 16 species of North America, including Mexico, the Caribbean, and Central America. These species are morphologically homogeneous and were considered by Woodson to both form a basal lineage and to retain ancestral characteristics of the genus. Ongoing phylogenetic research by M. Fishbein and coworkers indicates that series Incarnatae is indeed monophyletic if emended in two important ways: the exclusion of A. leptopus, and the inclusion of all (approximately) six species occurring in temperate South America. We investigated relationships in series Incarnatae, as emended, using DNA sequences from four plastid (rpl16 intron, trnC-rpoB spacer, trnG intron/trnS-trnG spacer, trnD-trnT spacer [including trnE and trnY]) and one nuclear (LEAFY intron 2) region. Unaligned, concatenated sequences total about 5 kb in length. We sampled 15 of Woodson’s 16 species of Incarnatae and five of six species of temperate South American Asclepias. Data were analyzed by parsimony, maximum likelihood, and Bayesian methods. We found strong support for a sister-group relationship between A. curassavica (widespread in the Neotropics and a pantropical weed) and A. nivea (endemic to the Antilles). This clade was strongly supported as sister to a well-supported clade containing all five samples of South American species. Together, these species were sister to a single clade containing all remaining species of series Incarnatae, which range from Canada to Panama. Relationships within this principally North American clade were not strongly supported by all methods of analysis. These results confirm the paraphyly of series Incarnatae (minus A. leptopus, as circumscribed by Woodson), to temperate South American Asclepias and suggest the dispersal of the genus from temperate North America to temperate South America.
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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 - University of Illinois Chicago, Department of Biological Sciences, M/C 066, 845 W Taylor Street, Chicago, Illinois, 60607, USA
Presentation Type: Recent Topics Poster
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM