A new species of Argentina (Rosaceae, Potentilleae) from Southeast Tibet, with reference to the taxonomic status of the genus

Argentina songzhuensis, a new species of tribe Potentilleae (Rosaceae) from Southeast Tibet, is described and illustrated. Placement of this species within Argentina was assessed based on morphological comparisons with related species and on phylogenetic analyses of nuclear ITS and plastid trnL-F sequences. The new species is similar to A. glabriuscula, but can be easily distinguished by its densely hairy leaflets, number of stamens (ca.10-12) and decurrent bases of the uppermost pair of leaflets. Our results support the generic status of Argentina and suggest that ventral stipular auricles may be a good synapomorphy for the genus. The recent transfer to Argentina of several Sibbaldia species as well as the genera Piletophyllum and Tylosperma is also confirmed by our molecular phylogenetic analyses. A taxonomic key to A. songzhuensis and other Argentina species in Tibet is provided.