Systematics Section / ASPT
Moore, Michael J. , Bell, Charles D. , Soltis, Pamela S. , Soltis, Douglas E. .
Using complete chloroplast genome sequences to resolve recalcitrant nodes in deep-level angiosperm phylogenetics.
Great progress has been made over the past decade in resolving relationships among basal angiosperm lineages, as demonstrated by the strong support for the sister relationship of Amborella, Nymphaeales, and Austrobaileyales to all other flowering plants. However, several other deeper nodes in the angiosperm tree of life have yet to be resolved. The branching order among Ceratophyllum, Chloranthaceae, eudicots, magnoliids, and monocots has been particularly fluid in previous phylogenetic analyses, with little support for any specific relationship among these taxa. The increasing number of complete angiosperm plastid genome sequences presents an opportunity to explore whether large data sets can resolve these relationships. We present phylogenetic analyses of 61 plastid protein-coding genes (~42,000 bp) derived from complete plastid genome sequences for 45 taxa, including at least one member of every major basal lineage of angiosperms. Parsimony analyses of combined and partitioned data sets are inconsistent in the placement of several taxa, in particular Ceratophyllum, which is characterized by a relatively long branch. In contrast, maximum likelihood (ML)-based analyses return a consistent topology regardless of combined or partitioned data, with moderate or strong support for all nodes in combined data set analyses. ML analyses support a sister relationship between Ceratophyllum and eudicots, with monocots sister to this clade. This Ceratophyllum + eudicots + monocots clade forms a strongly supported sister clade to a clade of Chloranthaceae + magnoliids. The extremely short branches separating these five lineages imply a rapid diversification, the potential timing of which is discussed. These short branches have also contributed to the difficulties in resolving the phylogenetic relationships among these lineages, particularly under parsimony. The topological consistency of ML estimates of phylogeny in our study is therefore encouraging because it suggests that a consistent and recoverable deep-level phylogenetic signal may be present across angiosperm chloroplast genomes for these nodes.
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1 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - Florida State University, School of Computational Sciences, Tallahassee, FL, 32306-4120, USA
3 - University of Florida, Florida Museum of Natural History, PO Box 117800, Gainesville, FL, 32611-7800, USA
4 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
large data sets.
Presentation Type: Oral Paper:Papers for Sections
Location: Boulevard C/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:15 AM