The dalbergioid legumes (Fabaceae): Delimitation of a pantropical monophyletic clade

A monophyletic pantropical group of papilionoid legumes, here referred to a s the "dalbergioid" legumes, is circumscribed to include all genera previou sly referred to the tribes Aeschynomeneae and Adesmieae, the subtribe Bryin ae of the Desmodieae, and tribe Dalbergieae except Andira, Hymenolobium, Va tairea, and Vataireopsis. This previously undetected group was discovered w ith phy logenetic analysis of DNA sequences from the chloroplast trnK (incl uding matK) and trnL introns, and the nuclear ribosomal 5.8S and flanking i nternal transcribed spacers 1 and 2. All dalbergioids belong to one of thre e well-supported subclades, the Adesmia, Dalbergia, and Pterocarpus clades. The dalbergioid clade and its three main subclades are cryptic in the sens e that they are genetically distinct but poorly, if at all, distinguished b y nonmolecular data. Traditionally important taxonomic characters, such as arborescent habit, free stamens, and lomented pods, do not provide support for the major clades identified by the molecular analysis. Short shoots, gl andular-based trichomes, bilabiate calyces, and aeschynomenoid root nodules , in contrast, are better indicators of relationship at this hierarchical l evel. The discovery of the dalbergioid clade prompted a re-analysis of root nodule structure and the subsequent finding that the aeschynomenoid root n odule is synapomorphic for the dalbegioids.