Phlogacanthus yangtsekiangensis, a new combination in Chinese Acanthaceae

The genus Cystacanthus was established by Anderson (1867: 457) and placed in tribe Ruellieae Dumortier (1829: 23) when published. In fact, it is closely related to Phlogacanthus Nees von Esenbeck (1832: 76, 99) and differs only in the corolla shape and indumentum. Thus, many authors merged Cystacanthus with Phlogacanthus (Benoist 1935, Imlay 1939, Brummit 1992, Mabberley 2008). But it was still recognized as a genus independent from Phlogacanthus by many recent authors (Scotland 1992, Scotland & Vollesen 2000, Hu 2002, Hu & Fu 2005, Wu et al. 2003, 2006, Hu et al. 2011). Our recently unpublished molecular analysis, however, showed that species of Cystacanthus are nested within Phlogacanthus and they might be treated as a single genus, Phlogacanthus. Phlogacanthus belongs to tribe Andrographideae Endlicher (1839: 707) and consists of about 35 species distributed in S and SE Asia (Scotland 1992, Scotland & Vollesen 2000, Mabberley 2008, McDade et al. 2008). In the recently published English version of the Flora of China (Hu et al. 2011), eight species were recognized in Cystacanthus. Among these, five species, i.e., Cystacanthus paniculatus Anderson (1867: 458), C. pyramidalis Benoist (1928: 907), C. abbreviatus Craib (1911: 438), C. vitellinus (Roxburgh 1820: 117) Y. F. Deng in Hu et al. (2011: 477) and C. colaniae (Benoist 1936: 109) Y. F. Deng in Hu et al. (2011: 477), already have names in Phlogacanthus; Cystacanthus yangtsekiangensis (Léveillé 1915: 6) Rehder (1935: 315), C. affinis Smith (1916: 103) and C. yunnanensis Smith (1916: 104), still need to be transferred to Phlogacanthus. Cystacanthus yangtsekiangensis, C. affinis and C. yunnanensis were described based on types from Jinsha Jiang Valley, N. Yunnan, China. Cystacanthus yunnanensis was considered to be different from C. yangtsekiangensis in the different indumentum. The character of the indumentum, however, is not sufficient to distinguish them as different species, as can be concluded after study of the type material. Cystacanthus affinis has abbreviated inflorescences and seems to be different from C. yangtsekiangensis. After comparing a large number of specimens, and after investigations in the field, it was reavealed that C. yangtsekiangensis has both abbreviated and elongated inflorescences and is therefore variable in this character. Therefore, we propose both Cystacanthus affinis and C. yunnanensis as synonyms of C. yangtsekiangensis. Currently, eight species in Phlogacanthus are recognized from China: P. abbreviatus (Craib 1911: 438) Benoist (1935: 712), P. colaniae Benoist (1936: 109), Phlogacanthus curviflorus (Wallich 1831: 9) Nees (1832: 99), P. paniculatus (Anderson 1867: 458) Imlay (1939: 128), P. pubinervius Anderson (1867: 508), P. pyramidalis (Benoist 1928: 907) Benoist (1935: 711), P. vitellinus (Roxburgh 1820: 117) Anderson (1867: 507) and P. yangtsekiangensis (Léveille 1915: 7) C. Xia & Y. F. Deng.