Saussurea sejilaensis (Asteraceae, Cardueae), a new species from southeastern Xizang, China

Saussurea sejilaensis (Asteraceae, Cardueae), a new species from Sejila Mountain in southeastern Xizang, China, is described and illustrated. Based on morphological characters and the current infrageneric classification, the new species is assigned to Saussurea subg. Amphilaena. Maximum likelihood (ML) and Bayesian inference (BI) analyses based on nuclear ribosomal internal transcribed spacer (nrITS) sequences recovered S. sejilaensis, S. ceterach, and S. leontodontoides as a strongly supported clade (UFBoot = 96; PP = 0.995). Morphologically, S. sejilaensis resembles S. pumila and S. leptolepis. It differs from S. pumila in having ovate to broadly ovate leaf blades with densely greyish-white to silvery tomentose abaxial surfaces and phyllaries in 3–4 rows, whereas S. pumila has narrowly ovate-elliptic to spatulate, glabrous leaf blades and phyllaries in 4–5 rows. It differs from S. leptolepis in its acaulescent habit, subentire to shallowly crenate leaf blades, a solitary capitulum borne near ground level at the centre of the leaf rosette, and a smaller campanulate involucre. Scanning electron microscopy showed that the pollen grains are elliptic in equatorial view and subcircular in polar view, with an echinate exine bearing numerous minute perforations, whereas the achenes are narrowly cylindrical with longitudinally striate-rugose surface ornamentation.