We present a phylogenetic analysis of a combined data set for 560 angiosperms and seven outgroups based on three genes, 18S rDNA (1,855 bp), rbcL (1,428 bp), and atpB (1,460 bp) representing a total of 4,743 bp. Parsimony analysis was expedited by use of a new computer program, the RATCHET. Parsimony jackknifing was performed to assess the support of clades. The combination of three data sets for numerous species has resulted in the most highly resolved and strongly supported topology yet obtained for angiosperms. In contrast to previous analyses based on single genes, much of the spine of the tree and most of the larger clades receive jackknife support >50%. Some of the monosulcates (magnoliids) form a grade followed by a strongly supported eudicot clade. The first-branching angiosperms are Amborellaceae, Nymphaeaceae, and a clade of Austrobaileyaceae, Illiciaceae, and Schisandraceae. The remaining monosulcates, except Ceratophyllaceae, form a weakly supported core clade comprising six well-supported subclades: Chloranthaceae, monocots, Winteraceae/Canellaceae, Piperales, Laurales, and Magnoliales. Ceratophyllaceae appear as sister to the eudicots. Within the well-supported eudicot clade, the lower eudicots (e.g., Proteales, Ranunculales, Trochodendraceae, Sabiaceae) form a grade, followed by the core eudicots, the monophyly of which is also strongly supported. The core eudicots comprise six well-supported subclades: 1) Berberidopsidaceae/Aextoxicaceae; 2) Myrothamnaceae/Gunneraceae; 3) Saxifragales, which are the sister to Vitaceae (including Leea) plus a strongly supported eurosid clade; 4) Santalales; 5) a caryophyllid, or Caryophyllales clade, which are sister to Dilleniaceae; 6) an asterid clade. The relationships among these six subclades of core eudicots do not receive strong support. This large data set has also helped place a number of enigmatic angiosperm families, including Podostemaceae, Aphloiaceae, and Ixerbaceae. This analysis further illustrates the tractability of large data sets and supports a recent, phylogenetically based, ordinal-level reclassification of the angiosperms based largely but not exclusively on molecular (DNA sequence) data.
ADDITIONAL KEY WORDS:-classification-molecular systematics-large data sets