Phylogenetics of the hamamelidae and their allies: Parsimony analyses of nucleotide sequences of the plastid gene rbcL

Over the past decade it has become increasingly clear that the angiosperm s ubclass Hamamelidae is polyphyletic. To examine phylogenetic affinities of various lineages in the complex and to evaluate the positions of lower hama melids in angiosperm phylogeny, we performed a parsimony analysis using nuc leotide sequences of the plastid gene rbcL from 134 species, including repr esentatives of 25 families that have traditionally been placed in the Hamam elidae; most rosid families; and selected members of the caryophyllids, ast erids, monocots, and magnoliids. Platanaceae, Eupteleaceae, Tetracentraceae , Trochodendraceae, Buxaceae, Didymeleaceae, and Myrothamnaceae occupy basa l positions in the eudicots, together with Ranunculales-Papaverales, Nelumb onaceae, Proteaceae, and Gunneraceae. Cercidiphyllaceae, Daphniphyllaceae, and Hamamelidaceae are placed among basal rosids, being closely related to Paeonia and Saxifragaceae s.s. and their allies. Nothofagaceae, Fagaceae, J uglandaceae, Ticodendraceae, Myricaceae, Betulaceae, and Casuarinacae form a monophyletic group, which in some trees is embedded in a large rosid clad e that includes many nitrogen-fixing species. Ulmaceae, Moraceae, Cannabace ae, Urticaceae, Cecropiaceae, and Barbeyaceae are also part of this "nitrog en-fixing clade," and they are related to Rhamnus, Elaeagnus, Dirachma, and Rosaceae. Leitneriaceae are clearly a member of Sapindales. Eucommiaceae f orm a clade with Aucuba and Garrya among the asterids.