The recently published analysis of atpB, rbcL, and 18SrDNA sequences (Soltis et al. 1999. Nature 402:402) strongly supports monophyly of the Rosales. This order contains about 6300 species in 9-11 families, all of which except Moraceae and Rosaceae have fewer than 1500 species. These genes place Rosaceae as sister to the remainder of the order, which consists of a trichtomy of Rhamnaceae, the weakly supported pairing of Elaeagnaceae + Barbeyaceae, and the well supported suborder Urticineae. Ulmaceae is the first branch within Urticineae, and Urticaceae is sister to a weakly supported assemblage of Moraceae + (Cannabaceae + Celtidaceae). In an attempt to clarify relationships within the Rosales, we use three chloroplast DNA sequences portions of the matK and ndhF genes and the trnL region that are more rapidly evolving than atpB, rbcL, and 18SrDNA. Our three genes total about 4400 aligned nucleotide sites, and our sample is nearly identical to the 18 genera in the combined atpB-rbcL-18SrDNA study. With sequences from Fabaceae as an outgroup, our three genes recover nearly the same topology as the atpB-rbcL-18SrDNA study, although there is less support for deeper branches in the Rosales tree, and the trichotomy is weakly resolved with the Rhamnaceae as sister to the Urticineae. The combined analysis of over 9000 aligned sites from atpB, rbcL, 18SrDNA, matK, ndhF, and trnL produces the same topology as the atpB-rbcL-18SrDNA study, including the trichotomy, but adds support to the Elaeagnaceae-Barbeyaceae and Moraceae-Cannabaceae-Celtidaceae clades. This topology provides a context for studies of character evolution in this morphologically diverse order.

Key words: matK, ndhF, phylogeny, Rosaceae, suborder Urticineae, trnL