A new species of Polygonum sect. Polygonum (Polygonaceae) from southwest of Türkiye

Polygonum uysalii (Polygonaceae), a new species from the transition zone between Mediterranean and Irano-Turanian floristic region of Türkiye is described based on morphological and molecular evidence. The new species is similar to P. ekimianum and P. salebrosum endemic to Türkiye, but it clearly differs by its ovate-broadly elliptic leaf (not linear–lanceolate to narrowly elliptic- suborbicular), 0.9 ̶ 1.6 mm length pedicel (not 2.1 ̶ 4.88 mm), dark brown ochrea at base (not pale brown) and trigonous fruit (not weakly trigonous only in upper part or ovate-elliptic). Diagnostic characters and phylogeny of the new species are discussed with respect to taxonomy and illustrations. Conservation status of the new species is also assessed according to field observations.