55 (4) • November 2006: 837–856 Qiu & al. • Basal angiosperm phylogeny Reconstructing the basal angiosperm phylogeny: evaluating information content of mitochondrial genes Yin-Long Qiu1, Libo Li, Tory A. Hendry, Ruiqi Li, David W. Taylor, Michael J. Issa, Alexander J. Ronen, Mona L. Vekaria & Adam M. White 1Department of Ecology & Evolutionary Biology, The University Herbarium, University of Michigan, Ann Arbor, Michigan 48109-1048, U.S.A.
[email protected] (author for correspondence). Three mitochondrial (atp1, matR, nad5), four chloroplast (atpB, matK, rbcL, rpoC2), and one nuclear (18S) genes from 162 seed plants, representing all major lineages of gymnosperms and angiosperms, were analyzed together in a supermatrix or in various partitions using likelihood and parsimony methods. The results show that Amborella + Nymphaeales together constitute the first diverging lineage of angiosperms, and that the topology of Amborella alone being sister to all other angiosperms likely represents a local long branch attrac- tion artifact. The monophyly of magnoliids, as well as sister relationships between Magnoliales and Laurales, and between Canellales and Piperales, are all strongly supported. The sister relationship to eudicots of Ceratophyllum is not strongly supported by this study; instead a placement of the genus with Chloranthaceae receives moderate support in the mitochondrial gene analyses. Relationships among magnoliids, monocots, and eudicots remain unresolved. Direct comparisons of analytic results from several data partitions with or without RNA editing sites show that in multigene analyses, RNA editing has no effect on well supported rela- tionships, but minor effect on weakly supported ones. Finally, comparisons of results from separate analyses of mitochondrial and chloroplast genes demonstrate that mitochondrial genes, with overall slower rates of sub- stitution than chloroplast genes, are informative phylogenetic markers, and are particularly suitable for resolv- ing deep relationships.