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 subclass Hamamelidae is polyphyletic. To examine phylogenetic affinities of various lineages in the complex and to evaluate the positions of lower hamamelids in angiosperm phylogeny, we performed a parsimony analysis using nucleotide sequences of the plastid gene rbcL from 134 species, including representatives of 25 families that have traditionally been placed in the Hamamelidae; most rosid families; and selected members of the caryophyllids, asterids, monocots, and magnoliids. Platanaceae, Eupteleaceae, Tetracentraceae, Trochodendraceae, Buxaceae, Didymeleaceae, and Myrothamnaceae occupy basal positions in the eudicots, together with Ranunculales-Papaverales, Nelumbonaceae, 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, Juglandaceae, Ticodendraceae, Myricaceae, Betulaceae, and Casuarinacae form a monophyletic group, which in some trees is embedded in a large rosid clade that includes many nitrogen-fixing species. Ulmaceae, Moraceae, Cannabaceae, Urticaceae, Cecropiaceae, and Barbeyaceae are also part of this "nitrogen-fixing clade," and they are related to Rhamnus, Elaeagnus, Dirachma, and Rosaceae. Leitneriaceae are clearly a member of Sapindales. Eucommiaceae form a clade with Aucuba and Garrya among the asterids.