Koenigia yatagaiana (Mori) T.C.Hsu & S.W.Chung, 2016

Hsu, Tian-Chuan & Chung, Shih-Wen, 2016, Two new combinations in Polygonaceae for the Flora of Taiwan, Phytotaxa 270 (1), pp. 69-70 : 69

Koenigia yatagaiana (Mori) T.C.Hsu & S.W.Chung , comb. nov.

≡ Polygonum yatagaianum Mori (1937: 25) .

Type:— TAIWAN. Taichung: Mt. Tugitaka , ca. 3250 m, 25 October 1936, K. Mori s.n. (holotype TAI! [sheet no. 118794 ], image available at http://tai2.ntu.edu.tw/specimen/specimen.php?taiid=118794 ; isotype: P! [barcode no. P00734209 ], image available at https://science.mnhn.fr/institution/mnhn/collection/p/item/p00734209?listIndex=26&listCount=908) .

Additional specimens examined: — TAIWAN. Ilan: En route from Chihyushan to Hsingta Camp , 2900–3300 m, 13 August 1993, C.H.Chen et al. 264 ( HAST . Taichung: Mt. Chihyu , 3000–3200 m, 7 August 2008, T.C.Hsu 1541 ( TAIF) ; 24 July 2012, T.C.Hsu 6076 ( TAIF) .

Note: — Polygonum yatagainum , a neglected species in both Flora of Taiwan ( Liu et al. 1976, Kuo et al. 1996) and Flora of China ( Li et al. 2003), is closely related to the Himalayan Koenigia delicatula (Maisner 1857: 127) Hara (1966: 70) , but differs in having smaller habits (up to 8 cm tall), usually solitary flowers, and 4-partite perianth. K. delicatula , on the other hand, has larger habits (up to 30 cm tall), usually clustered flowers, and 5-partite perianth ( Hedberg 1988, 1997, Li et al. 1998, 2003). We thus disagree with Hedberg (1997) who placed P. yatagaianum in synonymy under K. delicatula subsp. delicatula . Since very few data are available in previous literature, voucher specimens of K. yatagaiana are also cited here for reference as well as the type. Fan et al. (2013) suggested that Koenigia as defined by Hedberg (1997) and Li et al. (2003) is paraphyletic, and K. delicatula should be segregated into a new genus to keep the rest species of Koenigia s.str. monophyletic. It is possible that K. yatagaianum also belongs to their new genus due to its morphological similarity with K. delicatula . However, in a more recent systematic study, Schuster et al. (2015) disagreed the suggestion of Fan et al. (2013) but redefined an enlarged Koenigia to keep its monophyly, and a new genus for K. delicatula and K. yatagaianum is hence not necessary.