Synopsis of the tribe Stipeae (Poaceae) in Nepal

Abstract In Nepal the Stipeae consists of six genera: Achnatherum, Orthoraphium, Piptatherum, Ptilagrostis, Stipa, Trikeraia, and 15 species. Two new combinations, Ptilagrostis duthiei (Hook. f.) M.Nobis & P.D.Gudkova and Achnatherum staintonii (Bor) M.Nobis & P.D.Gudkova, are proposed, and new country records for Stipa klimesii, Ptilagrostis dichotoma, Ptilagrostis concinna and Achnatherum jacquemontii are reported. The records of Stipa roborowskyi, S. przewalskyi, S. capillata, S. consanguinea, S. mongholica, and S. sibirica, previously thought to occur in Nepal were based on misidentifications, and these have been excluded from the list of Nepalese Stipeae. We present keys for the identification of genera and species, and a checklist including information on nomenclatural types, regional and national distribution, and habitat. A lectotype is designated for Stipa brandisii Mez.


Introduction
The tribe Stipeae L. (feather grasses) is composed of extratropical and high-mountain grasses consisting of about 680 species distributed on all continents except Antarctica (Tzvelev 1977;Barkworth 2007;Romaschenko et al. 2008Romaschenko et al. , 2010Romaschenko et al. , 2011Romaschenko et al. , 2012Soreng et al. 2003, 2015, 2017, Nobis et al. 2019. It is an early divergent, highly specialized, monophyletic lineage within the subfamily Pooideae Benth. The Stipeae are characterized by their single-flowered spikelets without rachilla extensions, lemmas with apical awns where the awn is the result of fusion between the central and two lateral vascular traces, florets with three (rarely two) lodicules, and usually the palea is concealed by the lemma (if the palea is exposed when the floret is closed, then the palea is coriaceous (Roshevitz 1934;Tzvelev 1976;Freitag1985).
Although agrostologists have maintained a broad concept of the genus Stipa L. since its description (Hitchcock 1935, Clayton andRenvoize 1986;Freitag 1985;Columbus et al. 2019 and others), recent molecular phylogenetic studies suggest that ca. 34 genera should be recognized within the tribe (Hamasha et al. 2012;Nobis et al. 2019;Peterson et al. 2019). However, the species composition of some genera still requires further study.
All previous treatments of the Stipeae in Nepal have followed a broad generic concept. The Annotated checklist of the flowering plants of Nepal (Press et al. 2000, http://www.efloras.org/flora_page.aspx?flora_id=110) and the Flora of Mustang, Nepal (Ohba et al. 2008) Noltie), and S. krylovii Roshev. (Nobis et al. 2015;Gudkova et al. 2017a). Unfortunately, identification of Nepalese feather grasses is difficult due to the lack of recent, comprehensive, regional taxonomic studies. The main goal of this paper is to provide an identification key and checklist including information on types, nomenclature, distribution, and habitat for all Nepalese species of Stipeae.

Materials and methods
Our treatment is based on herbarium specimens deposited in BM, E, GOET, K, KATH, KRA, KUN, LE, M, NY, P (Thiers 2018). Each species is listed with complete nomenclatural and type information (the type specimens examined has exclamation mark after a herbarium code) synonyms, habitat requirements, and Nepalese and general distribution. The distribution within Nepal is given by District (Fig. 1). Elevation ranges and habitat requirements have been determined from herbarium specimen labels and from the literature.

Results and discussion
Detailed analyses of macro-and micromorphological structures of the lemma epidermis of Nepalese species of Stipeae confirmed that they form two main clusters, one with three subclusters (Fig. 2). The clusters correspond to the four lemma epidermal patterns (LEP): Stipa-like, Ptilagrostis-like, Piptatherum-like and Achnatherum-like (Fig.  3). The taxa from cluster I belonging to Stipa have long cells and hooks on the lemma epidermis in an ordered saw-like pattern (Romaschenko et al. 2012;Fig. 3a). Within subcluster A of cluster II, there are three genera, Ptilagrostis, Trikeraia and Orthoraphium ( Fig. 2), that have LEPs dominated by elongated basal cells, frequent silica bodies and cork cells h). However, the presence of deflexed, hard prickles in the case of Orthoraphium roylei (Fig. 3d), as well as 2-3 mm long awn-like lemma lobes   in the case of Trikeraia hookeri (Fig. 3e) are unique characters which distinguish them from other members of the subcluster. Subcluster B comprises species from the genus Piptatherum. These species differ from those in subcluster A in their extremely short callus, less numerous and rounded silica bodies on the lemma surface (Fig. 3f ). Taxa in subcluster C, all of which belong to the genus Achnatherum, have a maize-like type of LEP (Romaschenko et al. 2012), characterized by numerous silica bodies and very short basal cells (Fig. 3g-h). All of these species have lemmas distinctly longer than paleas.
Distribution in Nepal. Mustang.
Habitat. High mountain steppes and alpine mats, among subalpine shrubs and on rocky ledges.
Altitudinal range. 3600-4600 m. Note. These specimens were previously identified as P. concinna which also occurs in Nepal and which can be distinguished by its subequal glumes, lemma and palea. It has also been confused with Ptilagrostis bhutanica (Noltie) M. Nobis (basionym: Stipa bhutanica Noltie 1999: 289;Nobis et al. 2016), from Bhutan and China. However, these two taxa differ in the upper part of the awn which is scabrous in P. bhutanica and shortly pilose (with hairs over 0.5 mm long) in P. yadongensis.
Habitat. Open dry slopes, among shrubs and in Bamboo (Sinarundinaria sp.) thicket. Altitudinal range. 2400-4000 m. Note. Stipa brandisii was described by Mez (1921) based on a specimen housed at B but destroyed during the Second World War. In his original description of the species Mez (1921) reported that the species had been collected in 'Western-Himalaya, Kulla ([by] Brandis)', but did not provide further information about the date of specimen collection, number and place where it was housed. In the absence of the original material, the specimen at K (http://apps.kew.org/herbcat/getImage.do?imageBarcode=K000032092) was selected as lectotype by H. Freitag in 1984 and subsequently cited as the holotype (Freitag 1985). We designate this here as the lectotype.
Distribution in Nepal. Although we did not find any specimens of Trikeraia hookeri during this study we include it here because it is known from nearby regions (Freitag 1975, Wu andPhillips 2006), so it is very likely to be present in Nepal. Freitag (1985) reported this species from Nepal based on Sufed 104 (K), Mt. Everest, Tinkye palin, 4270 m, but this specimen appears to have been collected on the Tibetan side of Mt Everest.
Habitat. Scrublands, alpine mats. . These specimens are characterized by having 4-6 mm long lemma lobes, the awn arising below the middle of the lemma and ovary with two stigmas. Recently, Trikeraia oreophila was found to be conspecific with Sinochasea trigyna Keng (WCSP 2019). Morphological and molecular studies have shown that the genus Sinochasea is distinct not only from Trikeraia, but also from all the other genera of the tribe Stipeae, and therefore it was transferred to the tribe Phaenospermateae Renvoize & Clayton (Schneider et al. 2011;Romaschenko et al. 2012;Kellogg 2015).