EVANS, RODGER C. AND CHRISTOPHER S. CAMPBELL.* Department of Biological Sciences, University of Maine, Orono, ME 04469. - A multigene tree of the Rosales.
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