A molecular phylogeny of the early-branching Genistoid lineages of papilionoid legumes reveals a new Amazonian genus segregated from Clathrotropis

Molecular phylogenetic studies focused on the early-branching papilionoid legumes have revealed many new clades and supported several generic realignments, yet the monophyly of some of the constituent genera has remained unassessed. This is the case for the Amazonian genus Clathrotropis of the tribe Ormosieae. The genus, as traditionally circumscribed, comprises seven species of trees, including some of the most ecologically hyper dominant taxa across the Amazonian terra firme and seasonally flooded forests. Here we employed a Bayesian analysis of densely sampled nuclear ribosomal ITS/5.8S and plastid matK and trnL intron DNA sequences to evaluate the monophyly of Clathrotropis. All individual and concatenated analyses concurred in showing the non-monophyletic nature of Clathrotropis, whose species fall into three distantly related lineages: one, comprised of C. brachypetala, C. brunnea, C. glaucophylla and the ecologically dominant C. macrocarpa, is circumscribed here as the new genus Cabari; the two others, comprising C. paradoxa and the widespread C. nitida, are more closely related to Spirotropis of the tribe Ormosieae. Such phylogeny-based dismemberment of Clathrotropis is further supported by vegetative, floral, fruit, and seed characters. Although the genes analysed in this study have provided phylogenetically informative data supporting the need for a new circumscription of Clathrotropis, we suggest that future phylogenomic studies should seek to better resolve the relationships of the newly described genus Cabari across the phylogenetically recalcitrant early-branching nodes of the Genistoid clade.