Morphoanatomy and phylogenetics reveals a distinct species of Oxalis sect. Polymorphae (Oxalidaceae) from the Brazilian Atlantic forest

Morphoanatomical features can provide useful information for plant taxonomy. In Oxalis sect. Polymorphae (Oxalidaceae) there are currently 12 accepted species, mostly from the Brazilian Atlantic Forest, but the historical recognition of some infraspecific taxa may have resulted in underscored species richness. Integrated analyses of additional types of data are critical to evaluate if some taxa would be better recognized at species level. To evaluate this, we carried out leaf morphoanatomical analysis of O. neuwiedii subsp. neuwiedii and O. neuwiedii subsp. pardoensis and a phylogenetic analysis of nrITS sequences. Both leaf morphoanatomy and phylogenetics lend support to recognize O. neuwiedii subsp. pardoensis at species level. Leaflet venation pattern, epidermal cell outline, hair-covering, vascular conformation of the pulvina, and tissue organization in the midvein were the main morphoanatomical diagnostic features for the recognition of two species instead of a single one. A new rank and the second-step lectotypification are proposed for this taxon, raising to 13 accepted species in O. sect. Polymorphae.