Youngia zhengyiana (Asteraceae, Crepidinae), a new species from south China, with notes on the systematics of Youngia inferred from morphology and nrITS phylogeny

Youngia zhengyiana, a new species of Youngia sect. Mesomeris (Asteraceae: Crepidinae) from Guizhou province of south China is described and illustrated. The placement of this species within Youngia is assessed based on a molecular phylogenetic analysis of the nuclear ribosomal ITS and on morphological comparisons with related species. The new species can be easily distinguished by morphology from the only species known to possess 5 florets, Y. szechuanica. The infrageneric classification and the recently debated circumscription of Youngia are discussed in the light of the nrITS phylogeny, which includes several species for the first time. Pseudoyoungia is confirmed as a congener of Youngia. The redefined Youngia is still non-monophyletic with Lapsanastrum nested within it.