Calamagrostis hongii (Poaceae, Agrostidinae), a new species from southwestern China

Abstract Calamagrostis hongii, a new species of Calamagrostis (Poaceae) from southwestern China (S Chongqing, W Guizhou, Sichuan, SE Xizang, Yunnan), is here described and illustrated. It is similar to C. arundinacea and C. effusiflora in spikelet traits, but can be distinguished by its moderately or densely scabrous upper leaf surface with ribs covered by short, stiff, prickle hairs, and glabrous leaf sheaths, blades and collars. Nomenclature Deyeuxia zhongdianensis lacks Latin description or diagnosis and is an unavailable nomen nudum (naked name).


Introduction
Six species of Calamagrostis Adans. and thirty four species of Deyeuxia Beauv. were reported in the published taxonomic treatments for the "Flora of China" . Among them, 15 species of Deyeuxia and one species of Calamagrostis were considered to be endemic to China Huang et al. 2011Huang et al. , 2017. Twelve of these endemics occur in the mountains of SW China, which are recognized as a global biodiversity hotspot (Boufford 2014;Cai et al. 2019) and this region continues to produce species of grass new to science. Re-these specimens were collected in Yunnan, Sichuan and SE Xizang, with a few in adjacent Chinese provinces. For comparison, Calamagrostis effusiflora and Eurasian C. arundinacea (L.) Roth (in the "Flora of China" as Deyeuxia pyramidalis (Host) Veldk.) that show similarity in habit and spikelet traits, were also examined. We concluded that these plants represent an undescribed species new to science and we describe it here as Calamagrostis hongii Paszko & Bing Liu.

Materials and methods
We employed standard techniques for morphological studies of herbarium specimens from the CDBI, KUN, PE, US and W (acronyms follow Thiers 2017). All measurements were taken from the best-developed spikelets and leaf characteristics were determined on the 2 nd leaf from the top of the plants. The locality data in accounts below inferred from sources other than herbarium labels are placed in square brackets. The localities were sorted according to the county-level administrative division of the People's Republic of China. The distribution map was created with SimpleMappr (Shorthouse 2010) (Fig. 1). Specimens with the barcode numbers are accessible online via the PE Herbarium (http://pe.ibcas.ac.cn/en/), the National Plant Specimen Resource Center (http://www.cvh.ac.cn/), or the Muséum National d'Histoire Naturelle (https://science.mnhn.fr/institution/mnhn/collection/p/item/search). The data underpinning the analyses reported in this paper are deposited at GBIF, the Global Biodiversity Information Facility, https://www.gbif.org/dataset/c6dd8791-eaae-49f5-9c18-b4bc06a7357f.

Diagnosis.
Calamagrostis hongii is similar in habit and spikelet morphology to C. arundinacea and C. effusiflora, but differs in color and hairiness of the upper (adaxial) leaf blade surface. The upper leaf surface of Calamagrostis hongii is characterized by the grey color (vs. green or grey-green in C. arundinacea and C. effusiflora), the presence of moderately impressed veins forming ribs (vs. leaf surface flat or veins only slightly impressed in C. arundinacea or veins moderately or distinctly impressed, forming ribs in C. effusiflora), the presence of numerous prickle hairs covering the ribs (vs. lack of prickle hairs on veins or ribs of C. arundinacea and C. effusiflora) and the absence of hairs (vs. moderately or densely hairy in C. effusiflora and slightly or not hairy in C. arundinacea). Calamagrostis hongii is characterized by glabrous leaf sheaths, blades and collars. Description. Perennial grass, cespitose, without rhizomes. Culms 55-140 cm tall, erect, unbranched above, 3-4.5 mm in diameter near the base, nodes 3-5, glabrous below the panicle. Leaf sheaths glabrous; collar glabrous; ligules 1.9-10 mm long, acute; blades 5-55 cm long, 4.3-9.5 mm wide, flat, slightly ribbed with glabrous furrows and scabrous ribs, upper (adaxial) surface scabrous owing to the presence of short stiff prickles on ribs, gray or gray-green, lower surface slightly scabrous, green, scabrous along margins. Panicles 13-25 cm long, erect, open, or loosely contracted at maturity; proximal internode 0.6-3.7(-4.5) cm long; rachis with 3-7 branches per node; branches 4-10 cm, slightly scabrous, spikelet-bearing only beyond mid-length. Spikelets 3.8-6.6 mm long, 1-flowered, with one fertile floret with rachilla extension, laterally compressed, disarticulation above the glumes; glumes subequal or equal, glabrous, very weakly scabrid on keel, apex acuminate; lower glumes 3.8-6.6 mm long and 0.9-1.4 mm wide, 1-veined; upper glumes 3.5-5.9 mm long and 1.1-1.6 mm wide, 3-veined, 0.8-1.1 times as long as the lower glume; callus hairs 1.0-2.9 mm long, 0.3-0.6 times as long as the lemmas; lemmas 3.5-4.8 mm long, 5-veined, 0.7-1.0 times as long as the lower glumes, apex 4-toothed; lemmatal awn 5.3-7.8 mm long, arising from near base (0.06-0.15 way up the back) of the lemmas, exserted, slender and easily distinguished from the callus hairs, geniculate, with twisted column; paleas 2.8-4.5 mm long, subequal or equal to the lemma, 0.8-1.0 times as long as the lemmas; rachilla extensions 1.0-2.8 mm long, densely bearded with hairs 2.4-4.2 mm; stamens 3, anthers 1.3-2.6 mm long. Fl. Jul-Aug. Fr. Aug-Sep. Taxonomic note. Although Calamagrostis and Deyeuxia were revised for China only fourteen years ago in the "Flora of China"  it is necessary to present a new taxonomic account of these species because of the changes in generic circumscription and the description of new species. Calamagrostis hongii is the third new species of Calamagrostis reported from China since the publication of the "Flora of China". This new species is probably a member of the C. arundinacea complex and it is similar to C. arundinacea and C. effusiflora in habit and spikelet traits, including size of glumes, lemmas and paleas, presence of well-developed rachilla prolongation and a geniculate lemma awn with a twisted basal column, lemma awn length and its insertion on the lemma back (near the base to the lower 1/3). However, they differ in several diagnostic characteristics. Prior to this study, most of the specimens currently identified as C. hongii had been identified as Deyeuxia pyramidalis [= Calamagrostis arundinacea]. The detailed revision of this group of species by the present authors showed that the upper surfaces of the leaves of C. hongii are unique. They are gray in color and moderately or densely scabrous and characterized by the presence of moderately impressed veins forming ribs that are slightly or densely covered by numerous prickle hairs (Fig. 3). Such prickle hairs are absent from the upper surfaces of the leaf blades of C. arundinacea and C. effusiflora. The upper surface of the leaf blade of C. arundinacea has veins that are only slightly impressed and the leaf blade surface is almost flat and hairless or covered by scattered macro hairs (Fig. 4), whereas C. effusiflora has veins slightly to distinctly impressed, forming ribs that are usually moderately to very densely hairy (Fig. 5). All three species have prickly leaf edges. The prickle hairs have thick walls that can be silicified. For additional diagnostic characteristics see Table 1. The designation Deyeuxia zhongdianensis L. Liou (Liou 1994(Liou : 2235 was described without Latin description or diagnosis. From January 1, 1935, to December 31, 2011, one or both had to be in Latin, thus Deyeuxia zhongdianensis is nomenclaturally invalid and therefore unavailable under the Article 39.1 of the ICN (Turland et al. 2018). Liou (1994Liou ( : 2235) cited Feng's collection no. 3326 from Zhongdian County (now Shangri-La) in Yunnan Province, but the herbarium was not specified by the author. In PE we located three herbarium sheets (PE01854125, PE02108399, PE02108400) collected at Mt. Wuzhujun at Shangri-La City (former Zhongdian Co.) in Yunnan Province. We identified Feng's collection as C. hongii.  incorrectly synonymized Calamagrostis zhongdianensis with Deyeuxia pyramidalis (= C. arundinacea).

Vernacular name. 洪氏野青茅(Chinese), Hong's Bent-grass (English).
Etymology. The specific epithet honors Professor De-Yuan Hong, the Academician of Chinese Academy of Sciences (CAS) (State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, CAS, Beijing, China) for his outstanding achievements in systematics, morphology, cytology, ecology and molecular evolution. The second author thanks Professor De-Yuan Hong for his continuous support during her multiple research visits to the Chinese herbaria as part of an exchange program between the Polish Academy of Sciences and the Chinese Academy of Sciences, in order to study the herbarium collections of Calamagrostis and Deyeuxia for the "Flora of Pan-Himalaya".
Distribution and habitat. Calamagrostis hongii is endemic to south-western China. It is centered on the northern part of Yunnan and southern part of Sichuan and adjacent regions in south-western and central China, such as southern Chongqing, western Guizhou, central Sichuan and south-eastern Xizang. Its distribution covers the Southern Hengduan Mts and western and northern part of Yungui Plateau. A dot map provided here (Fig. 1) shows it to be common (or at least commonly collected) in northwestern Yunnan, with three dots along the Chinese border with Kachin State of Myanmar, where it may also occur. Calamagrostis hongii is restricted to the Sino-Himalayan subkingdom, primarily the Yunnan Plateau and Hengduan Mountains (Peng andWu 2013, Tang 2015). The species occurs in the montane belt from circa 1800 m to 3350 m a.s.l., in grasslands, among bushes, forest edges and in mixed Pinus yunnanensis forests.
Phenology. Calamagrostis hongii flowers from July to August and is in fruit from August to November.
Additional specimens examined.