The Bowdichia clade of Genistoid legumes: Phylogenetic analysis of combined molecular and morphological data and a recircumscription of Diplotropis

The Neotropical Bowdichia clade (Leguminosae: Papilionoideae) comprises four genera, Bowdichia, Diplotropis, Guianodendron, and Leptolobium, which are sister to the core Genistoid clade. Bowdichia and Diplotropis at one time were treated as a single genus, whereas Guianodendron and Leptolobium have been synonymized with the distantly related Dalbergioid genus Acosmium because of shared radial floral symmetry. We combined and analysed morphological and molecular data including the nuclear ribosomal internal transcribed spacers (ITS; including ITSI/5.8S/ITS2) and two chloroplast DNA (matK, trnL intron) regions in order to evaluate the monophyly of each genus and the Bowdichia clade. A combined parsimony analysis strongly supported the monophyly of Bowdichia, the paraphyly of Diplotropis, and the independent evolution of radial floral symmetry in Guianodendron and Leptolobium. Leptolobium is sister to Bowdichia and Guianodendron is nested within Diplotropis s.l. Diplotropis is here recircumscribed as to encompass the monophyletic Diplotropis sect. Diplotropis and it is suggested that D. sect. Racemosae deserves segregation into a new genus. Radial floral symmetry has been overemphasised in previous classifications by taxonomists who did not recognize its evolutionary lability. This has resulted in non-monophyletic circumscriptions of genera such as Acosmium.