Molecules, morphology, and Dahlgren's expanded order Capparales

Nucleotide sequences for the chloroplast gene rbcL have been obtained for three species of Salvadoraceae and for the unispecific Pentadiplandraceae, thus completing a survey of all known mustard-oil families. Phylogenetic analyses of the sequences based on maximum parsimony reveal two separate lineages of plants that produce mustard oil glucosides. A major mustard-oil clade comprises the core capparalean families of Brassicaceae, Capparaceae, Gyrostemonaceae, Resedaceae, and Tovariaceae and includes Akaniaceae, Bataceae, Bretschneideraceae, Caricaceae, Koeberliniaceae, Limnanthaceae, Moringaceae, Pentadiplandraceae, Salvadoraceae, and Tropaeolaceae. A second unrelated lineage consists of the genus Drypetes, traditionally placed in Euphorbiaceae. The major mustard-oil clade recovered from the rbcL analysis is congruent in many topological aspects with that found in a recent cladistic study of morphological characters, and in turn the molecular and morphological results confirm Dahlgren's radically expanded Capparales. An approach combining molecular and morphological evidence yields robust support for several lineages within this major mustard-oil clade.