Igniting Oxalis (Oxalidaceae) diversity in Espírito Santo, Brazil: a new endemic species of Oxalis subg. Thamnoxys from the Atlantic Forest hotspot

Abstract The Brazilian Atlantic Forest is one of the hottest hotspots of plant diversity and endemism. Recent taxonomic investigations have uncovered previously overlooked diversity in Oxalis (Oxalidaceae) in Brazil, especially within O. subg. Thamnoxys . Espírito Santo, a small southeastern Brazilian state located entirely within the Atlantic Forest, harbors a high number of endemic species of Oxalis . In this study, we describe a new species endemic to the central mountainous region of this state. Phylogenetic inference using nrITS sequences recovers the new taxon within O. sect. Thamnoxys . The new species can be distinguished from others of the section by the combination of the young stem with very abundant, patent to ascending and descending, non-glandular hairs, sometimes intermixed with sparse to moderate long, pluricellular, hyaline hairs, the leaves green or purplish, the terminal leaflet blade elliptic to ovate or widely ovate, with the apex rounded, the pedicel glabrous, the bracts and floral bracts pubescent and the yellow flowers. Anatomical observations reveal characters consistent with those previously documented for O. sect. Thamnoxys . We provide anatomical and taxonomic notes, as well as an identification key for the species of O. sect. Thamnoxys in Espírito Santo, and a preliminary assessment of its conservation status.