Relationships among core eudicot clades (the asterid, rosid, Caryophyllales, Santalales, Berberidopsidales, and Myrothamnaceae/Gunneraceae clades) remain one of the last major questions of deep-level phylogeny in the angiosperms. To resolve these relationships, we assembled a large data set of entire 26S ribosomal DNA sequences for approximately 250 angiosperms. The 26S rDNA is just under 3.4 kb in length and consists of conserved core areas, as well as more rapidly evolving expansion segments. Because of is length and regions with different evolutionary rates, it appears to be highly useful for resolving relationships at this level. We constructed several different data sets and analyzed them using parsimony: 1) 26S rDNA sequences were added to the existing 567-taxon matrix (Soltis et al.), 2) a smaller data set was constructed for only those angiosperms for which all four genes were available. We also used a compartmentalization approach, reconstructing ancestral sequences for major clades. Our preliminary analyses provide additional support for the major core eudicot clades and the relationships of early-branching eudicots.

Key words: 26S rDNA, angiosperms, eudicots, phylogeny