Systematics Section / ASPT
Yuan, Yaowu , Olmstead, Richard .
Viewing the Transition from Polyphyly to Paraphyly to Reciprocal Monophyly in Verbena (Verbenaceae): Is There an Overlooked Advantage of ITS/ETS in Species-level Phylogenetics?
Lineage sorting is a well-known process to cause widespread incongruence among gene trees. With regard to allelic relationships within two sister taxa, lineage sorting can lead to three possible phylogenetic outcomes: (1) Polyphyly; (2) Paraphyly; (3) Reciprocal monophyly. We demonstrate this lineage sorting process in the genus Verbena, a monophyletic group comprising some 27 species in North America and 18 species in South America. Nuclear Phot2 gene trees suggest both South and North American Verbena are polyphyletic. Nuclear waxy gene trees suggest S. American Verbena are paraphyletic in relation to the monophyletic N. American Verbena. Chloroplast gene trees suggest South and North American Verbena are reciprocally monophyletic. The pattern of these gene trees indicate the recent diversification of South and North American Verbena and that lineage sorting has not been completed at most nuclear gene loci, yet has been completed for the chloroplast genome due to its 4 times smaller effective population size. These hypotheses can be best tested with nuclear genes that coalesce faster than a typical single or low copy nuclear gene. The tandem-repeated ribosome DNA (ITS/ETS) has been used extensively in species-level phylogenetics, but the fast-coalescent characteristic of these DNA has been largely overlooked. Highly concerted evolution accelerates the lineage sorting process of the ITS/ETS region by continuously eliminating allelic polymorphisms. Supporting our hypotheses, the ITS/ETS gene tree also suggests that South and North American Verbena are reciprocally monophyletic. These results illuminate this largely overlooked advantage of ITS/ETS in plant species-level phylogenetics.
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1 - University of Washington, Department of Biology, Po Box 35-1800, Seattle, Washington, 98195-1800, USA
2 - University of Washington, Department of Biology and Burke Museum, Box 355325, Seattle, WA, 98195, USA
Presentation Type: Oral Paper:Papers for Sections
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 2:00 PM