A new species of Cotoneaster (Rosaceae) from western Sichuan, China.

Cotoneaster densiflorus, a new species of Rosaceae from western Sichuan, China, is described and illustrated. Morphologically, we inferred that the new species belongs to Cotoneaster Ser. Salicifolii sensu Yü et al. (1974) in the Flora of China and Fryer and Hylmö (2009). This species is most similar to C. salicifolius, but differs in its leaf blade of ovate-lanceolate to obovate shape (vs. elliptic-oblong to ovate-lanceolate), smaller lengthwidth ratio of 2.37 ± 0.31 (vs. 3.17 ± 0.32), slightly conduplicate (vs. not conduplicate), less lateral veins of 6–8 pairs (vs. 12–16 pairs), upper surface slightly rugose (vs. rugose), leaf margin plane (vs. revolute), lower surface densely grey tomentose (vs. grey tomentose, with bloom), greater corolla diameter of 7–9 mm (vs. 5–6 mm), styles 2 (vs. 2–3), pyrenes 2 (vs. 2–3), larger pollen grains P/E values of 2.05 ± 0.12 (vs. 1.19 ± 0.05) and leaf epidermis type W (vs. type I). Based on phylogenetic analysis of the whole chloroplast genome, C. densiflorus is sister to C. rhytidophyllus, but distantly related to C. salicifolius. [ABSTRACT FROM AUTHOR]