First record of Poa scabriculmis N. R. Cui (Poaceae) for the flora of Pan Himalayas

Poa scabriculmis N.R. Cui, 1987, is known as endemic species of alpines of Kunlun Mountains (Xinjiang Province, NW China). Later, in Flora of China, it was treated as subspecies of polytypical species P. albertii Regel, and sinonimized with other four relative species. In this work we restore the status of this species and present its new occurrence in Sichuan province (China). This paper present taxonomic notes, morphological description, habitat, and the current geographic distribution for P. scabriculmis


Introduction
Bluegrass -PoaL. -is one of the most wide spread and polymorphic genus of grasses. It contains about 500 species, which grow mainly in temperate and arctic regions [1]. Besides being common species in temperate floras, they play a significant role in plant communities, being the dominant species in meadows and steppes [2]. The section Stenopoa Dumort. is one of the most numerous, polymorphic and difficult. The species of this section are distributed primarily in Eurasia, particularly in the mountains of Asia [3]. Hybridization and apomixis have resulted in high morphological and karyological diversity, which has led to recognition of many new species. Lack of detailed information about many of the species currently makes it impossible to confirm or deny the appropriateness of recognizing them as species so most treated as a members of aggregates, which are thought to consist of closely related species. The dwarf Asian alpine species seem to be one of the most complicated groups. P.N. Ovchinnikov, who revised Poa for Flora of Tajikistan [4], noted that significant morphological similarity between the many species of bluegrasses is partly a consequence of their being very poorly represented in herbaria. As a result, not only do we lack information on their geographic distribution, it is difficult to evaluate their appropriate taxonomic rank [5].
Poa scabriculmis used to be known only from alpine region of the Kunlun Mountains and it was considered to be endemic to Xinjiang Province [6,7,8]. Later, in Flora of China, in accordance with accepted species concept, it was treated as subcpecies of polytypical species P. albertii Regel, 1881, and sinonimized with P. koelzii Bor, 1948, P. indattenuata Keng ex Keng f. et G.C. Song, 1994, P. rangkulensis Ovchinnikov et Chukavina, 1958, andP.roemeri Bor, 1970. In this work, we restore the status of this species and present its new occurrence ( Fig. 1) in Hengduan Mountains (Sichuan province, China).

Material and methods
In the summer of 2015 the II Sichuan expedition was organized by the Institute of Botany, CAS (Beijing, China) to study the flora Hengduan Mountains. It was carried out within the frame of the international project "Flora of the Pan-Himalayas", and covered the area proximally within N 27. The Hengduan Mountains, with elevations range from 1,300 to 6,000 m, support a range of habitats, from subtropical to temperate to montane biomes. It provides a very complex landscape with a high degree of biological diversity. The mountains are largely covered by subalpine coniferous forests [9], with alpine grasslands above the tree line.
This paper is based on observations made during fieldwork, conducted in August-September in Hengduan Mountains, and examination of specimens from BM, CDBI, E, K, KUN, LE, PE, SZ, XJA, XJBI, and XJNU. The samples of dwarfish Stenopoa from Tibet and adjacent area for comparison of indumentum, were kindly provided by Dr. R. J. Soreng (Smithsonian, USA) and Prof. Dr. G. Miehe (Philipps-Universität, Germany). The collections, obtained in the fieldwork were deposited in PE, SZ, KUN and TK. Nomenclatural information developed from our work has been shared with Dr. R. J. Soreng who has made it available via TROPICOS [10].

Discussion
Poa scabriculmis N.R. Cui was described as P. scabristemmed D.F. Cui [12] from the samples collected in alpine meadows of Kunlun in Chinese province Xinjiang, ca N 36.5 o E 81 o [10]. Later its name was corrected as P. scabriculmis by L. Liu [8]. In Flora of China [13], where a polytypic species concept was accepted and hybrid complexes treated as polytypic species, it and four other species (P. koelzii, P. indattenuata, P. rangkulensis, and P. roemeri) were treated as synonyms of the polytypic P. albertii, as a P. albertii subsp. kunlunensis, because this taxon was the first one, described at subspecies rank.
The characters of stem epidermis are frequently used to differentiate taxa within Stenopoa [2,14,15]. The detaled additional research of stem epidermis within dwarf species of Stenopoa has confirmed the unique characters of P. scabriculmis.
Indeed, very scabrid surface of the whole cauline internodes, caused by the dense pricles along the stem, was characteristic for P. scabriculmis. This character was constant in observed population of this species, found in Sichuan, and was quite rare and found only in individual specimens within populations of other similar species.
In Flora of Pan Himalayas, another concept is accepted in order to provide a stronger scientific basis for conservation of local biodiversity throughout this large and poorly known region. In this situation, a narrower species concept was adopted, and hybridogenous complexes were treated as aggregates, (aggr.). These aggregates are not formal taxa but groups of species with similar characteristics and, it is thought, of similar origins. Using such informal designation "aggregate" helps highlight areas that merit further research [16]. In accordance with such a treatment, and taking into account the unique anatomical characteristics of stem epidermis, P. scabriculmis was recognized as a species within aggr. P. albertii, members of which are thought to have arisen from hybridization between P. attenuata Trin., 1835, s.l. and P. glauca Vahl, 1790 [16].
Pan Himalayas cover the territory of Himalaya and adjacent mountain regions, from Wakhan corridor and North-Eastern Hindu Kush eastwards to the Hengshuan Mountains. The area in Kunlunshan, where P. scabriculmis was described, is outside the Pan Himalayas. Our discovery expands the distribution of P. scabriculmis and expands the area of species known from Sichuan and the Pan Himalayas.