Gymnostachyum morsei (Acanthaceae: Andrographideae), a new species from Guangxi, China
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
Gymnostachyum morsei (Acanthaceae: Andrographideae), a new species from Guangxi, China Yunfei Deng1,2 , Yunhong Tan2,3, Zheli Lin1 & Yunfeng Huang4 Summary. A new species, Gymnostachyum morsei Y.F.Deng, is described from Guangxi, China. A morphological description, taxonomic comments, distribution and habitat data, preliminary conservation status, illustration, and key to Chinese species in the genus are provided. The new species grows on rocks in limestone hill forest. It is similar to G. subrosulatum H.S.Lo, but differs in having lanceolate leaves with a narrowly cuneate base decurrent onto the petiole, and a trifurcating racemose inflorescence (vs suborbicular to broadly cordate leaves with a slightly cordate to rounded base, and a thyrse inflorescence in G. subrosulatum). Key Words. Asia, conservation status, limestone, taxonomy.
Introduction The genus Gymnostachyum Nees belongs to the family Acanthaceae and comprises 30 – 50 species distributed in the tropical regions of Asia (Hu et al. 2011; Prabhukumar et al. 2015; Mabberley 2017). Traditionally, it is placed in tribe Andrographideae or subtribe Andrographinae together with Andrographis Nees, Cystacanthus T.Anderson, Diotacanthus Benth., Graphan dra J.B.Imlay, Haplanthodes Kuntze, Indoneesiella Sreem. and Phlogacanthus Nees (Lindau 1895; Bremekamp 1965; Scotland 1992; Scotland & Vollesen 2000; McDade et al. 2008). Gymnostachyum is characterised by the characters of herbaceous or subshrubby habit, leaves entire, inflorescences of racemes, spikes or panicles, bracts and bracteoles shorter than the calyx, corolla 2-lipped, the upper lip 2-lobed and lower lip 3-lobed, stamens 2, the antherthecae usually single-spurred at the base, staminodes absent, ovary with 3 - several ovules per locule, capsule cylindrical, and seed compressed, covered with hygroscopic hairs (Lindau 1895; Chu 1991; Hu et al. 2011). However, the generic delimitation in tribe Andrographideae is controversial because of the use of different characters. The genus Cystacanthus was considered to be an independent genus from Phlogacanthus by the corolla tube abruptly inflated near the middle and usually bent c. 90° (vs the corolla tube cylindric and straight or slightly curved) (Scotland 1992; Scotland & Vollesen 2000; Hu et al. 2011). Recent molecular evidence showed that the species of Cystacanthus are nested within Phlogacanthus
(Deng, unpublished data), and it was therefore reduced to the synonymy of Phlogacanthus (Benoist 1935; Imlay 1939; Brummitt 1992; Xia & Deng 2013). Indoneesiella is reduced to Andrographis from which it differs only by the number of ovules and seed (Cramer 1996). Gnanasekaran et al. (2016) resurrected Haplanthus Nees from Andrographis by the characters of the corolla tube curved (vs straight), upper lip deeply 2-lobed (vs emarginate or minutely 2-lobed), stamens included (vs exserted), filaments pouched at apex (vs not pouched at apex), anther pilose or woolly only at the base of the connective (woolly throughout the con
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