A new species for the legume genus Chamaecrista (Fabaceae, Caesalpinioideae) supported by molecular, morphological, and anatomical data

Chamaecrista oligandra from the Brazilian Cerrado, the most diverse savannah and one of 34 hot spots of the world, is herein described, illustrated, and compared with C. flexuosa var. flexuosa and C. parvistipula, its morphologically similar congeners. The flowering and fruiting, environmental preferences, distribution map, images, and preliminary conservation status of the new species are provided. Additionally, leaf anatomy and scanning electron microscopy of the leaf petiolar nectaries of the new species and the two putative closest relatives were compared. A phylogeny based on the noncoding plastidial (trnL-trnF) and nuclear ribosomal internal transcribed spacer indicated the proper placement of C. oligandra sp. nov. in Chamaecrista sect. Chamaecrista ser. Flexuosae, which is a taxonomic group that includes sub-shrubby species with underground systems conspicuously developed, leaflets with palmate-dimidiate venation, and flowers in an axillary fascicle. A key to identify species of the C. ser. Flexuosae series is provided to facilitate recognition of species that are distributed in open areas of the Brazilian Cerrado and frequently misidentified in collections.