A phylogenetic analysis of Rhamnaceae using rbcL and trnL-F plastid DNA sequences

Previous tribal classifications of Rhamnaceae have been based on fruit char acters, resulting in the delimitation of large and otherwise heterogeneous groups. We evaluated the most recent classification with DNA sequences of t wo regions of the plastid genome, rbcL and trnL-F, from 42 genera of Rhamna ceae and representatives of the related families Elaeagnaceae, Barbeyaceae, Dirachmaceae, Urticaceae, Ulmaceae, Moraceae, and Rosaceae. The trnL-F tre es have higher consistency and retention indices than the rbcL trees, and p atterns of change in rbcL and trnL-F are compared. The closest relatives of Rhamnaceae are Dirachmaceae and Barbeyaceae, followed by the urticalean fa milies. The plastid trees support the monophyly of the family and provide t he basis for a new tribal classification. Three strongly supported clades a re identified, but morphological characters could not be found to underpin a formal taxonomic description of these three clades as subfamilies. We the refore only recognize groups that are also defined by morphological charact ers. The biogeography of Rhamnaceae is discussed with reference to the mole cular trees.