Taiwania 62(3): 315-320, 2017 DOI: 10.6165/tai.2017.62.315 Taxonomic notes on the dwarf bluegrasses (Poa L., Poaceae) of section Stenopoa in Pan-Himalayas Marina Vladimirovna OLONOVA1*, You-Sheng CHEN2, Sabine MIEHE3, Keshab Raj RAJBHANDRI4 and Mary BARKWORTH5 1. Tomskij gosudarstvennyj universitet, Biological institute 36, Lenin ave. Tomsk 634050, Russian Federation. 2. Institute of Botany, The National Herbarium (PE) 20 Nanxincun, Xiangshan, Beijing, Beijing 100093, China. 3. Utah State University, Intermountain Herbarium, 5305 Old Main Hill, Logan, Utah 84322-5305, USA. 4. Tribhuvan University, Central Department of Botany, Kirtipur, Kathmandu, Nepal. 5. Philipps-Universität Marburg, Marburg, Hessen, Germany. * Corresponding author's email: [email protected] (Manuscript received 9 February 2017; accepted 23 May 2017; online published 27 July 2017) ABSTRACT: The dwarf forms of Stenopoa (height 5–15 cm) which are common in alpine belt of the Pan-Himalayas, represent one of the most problematic groups in the genus. Ten dwarf species of Stenopoa have been recorded for the area under consideration: P. attenuata Trin, P.glauca Vahl, P. litvinoviana Ovcz., P. albertii Regel, P. koelzii Bor, P. lahulensis Bor, P. poophagorum Bor, P. arnoldii Melderis, P. mustangensis Rajb., and P. roemeri Bor. At least 6 other taxa have been mentioned as synonyms of these species. Comparative examination of many specimens of this group using a morphogeographic approach supports recognition of 10 species, which belong to 3 species aggregates: aggr. P. attenuata, aggr. P. glauca and aggr. P. albertii. Taxa in aggr. P. albertii are thought to have originated from hybridization between species of aggr. P. attenuata and aggr. P. glauca. Our research leads us to recommend recognizing P. roemeri, P. koelzii, P. mustangensis, P. rangkulensis Ovcz., P. scabriculmis N.R. Cui, P. tshuensis (Serg.) Olonova and P. indattenuata Keng as species; three of them have been recorded from the Pan-Himalayas. Poa koelzii is included in aggr. P. attenuata because of its similarity to that species. A key for identifying the taxa is presented. One new combination, Poa scabriculmis subsp. kunlunensis (N.R. Cui) Olonova, is presented. KEY WORDS: Grasses, Poa, Pan-Himalayas, Systematics. INTRODUCTION which are closely related to each other. The dwarf forms of sect. Stenopoa (height 5-15(25) cm), which The aim of any systematic treatment is to are common and characteristic in the upper mountain understand and reveal the morphological and genetic and alpine belt of Asia, including the Pan-Himalaya diversity in a group of taxa and represent it in a (alpine regions of SE Tajikistan, NE Afghanistan, N hierarchical structure. Such work often culminates in Pakistan, N India, Nepal, SW China, Bhutan and N the development of identification keys that reflect the Myanmar), represent one of the most problematic of recommended treatment. Such keys can emphasize such groups. (Tzvelev 1976; Dickoré 1995). Ten dwarf readily discernible characters even if these were given species of sect. Stenopoa have been reported for the little weight in forming the groups as, for example, Pan-Himalayas: P. albertii Regel, P. arnoldii Melderis, when morphological keys are written to identify groups P. attenuata Trin, P. glauca Vahl, P.koelzii Bor, P. identified by molecular phylogenies. Molecular work lahulensis Bor, P. litvinoviana Ovcz., P. mustangensis can provide more detailed information about the genetic Rajbh., P. poophagorum Bor, and P. roemeri Bor (Bor diversity present but, if they are to be used effectively 1952, 1970; Cope 1982; Ling, Liu 1987; Rajbhandari and efficiently, they must be based on detailed 1991; Noltie 2000; Liu 2003; Sun 2003; Kandwal et al., morphological and geographical knowledge of the 2003; Sekar et al. 2004; Zhu et al. 2006; Koba 2008; plants involved. The goal of our work was to develop Brecle et al. 2013). At least 6 names have been such knowledge for a problematic group of species mentioned as being synonyms of these species. Three belonging to Poa L. sect. Stenopoa Dumort. in of these names (P. arnoldii, P. mustangensis and P. Pan-Himalaya. poophagorum,) appear to refer to well characterized The systematic treatment of Poa L., particularly taxa with distinct distributions but the status of the Poa sect. Stenopoa, is known to be difficult. The remainder, particularly P. koelzii and P. roemeri, needs difficulty arises from the fact that, because of the additional research and consideration. prevalence of hybridization (Tzvelev 1976; Probatova Some populations of dwarf Stenopoa taxa have 2007) and apomixis (Stebbins 1941; Gustaffson 1947; been recognized as species although there is little Clausen 1954, 1961), we deal not so much with information about their variability, the heritability of individual species but with hybridogenic complexes their distinguishing features, or even their relationship 315 Taiwania Vol. 62, No. 3 and identity of their parental species. There are no treated as polytypic species. karyological data, no molecular data, and no Preparation of a treatment for the new, large scale information about how the species would compare if project, “Flora of the Pan-Himalaya,” demands that a grown under controlled conditions. In other words, the new treatment is to be prepared, one that reflects data available data on Asiatic alpine bluegrasses not only acquired since completion of the treatment in the “Flora precludes conducting systematic research at the γ level, of China” so that it can provide a scientific basis for which uses all available biological information, conservation of local biodiversity throughout this larger including the molecular data for revealing the and poorly known region. We find it useful, in this evolutionary rates and trends, but often also at the β situation, to adopt a narrower species concept but level, which attempts to place the species into a natural identifying as species aggregates, (aggr.), not formal system. It is difficult to argue for the recognition of taxa, groups of species that have similar characteristics. species based solely on morphological differences, Using the informal designation “aggregate” helps often very slight differences although the frequent lack highlight areas that that merit further research. It would of any other kind of data makes this, by necessity, a be possible to present these as formal taxa, possibly common practice. Nevertheless, in the absence of any superspecies, to reflect new interpretations of the other kind of information, it is also difficult to support affinities of the taxa involved but it seems unwise to placing them in synonymy even if the differences are add more names to the many that already exist until slight. Bluegrasses, like other grasses, have few more information is available. prominent markers of their evolutionary branches. The dwarf members of sect. Stenopa differ from each other MATERIALS AND METHODS primarily by the distribution of their lemma indumentum and the presence or absence of a tuft of This paper is based on observations made during hairs on the callus. These features are not reliable fieldwork, conducted over several seasons, in Siberia markers of relationship because they may have arisen (Altai, W Sayan), Tajikistan (Gissaro-Darvaz, Alay and independently or been acquired through hybridization. Pamir), China (Xinjiang and Sichuan) and examination On the other hand, minor morphological differences of specimens from BM, BRY, C, E, HAL, K, KUN, L, among geographically isolated populations can hide LE, MW, NS, NSK, PE, SZ, TAD, TK, US, UTC, XJA, deep genetic differences. Failure to recognize them XJBI, XJNU. The field work led to the collection of because their differences, in the absence of additional 2,500 specimens that have already been deposited in supporting information, are deemed too slight and can TK and additional samples, collected in Sichuan, that lead to lack of concern for their conservation and even will also be deposited in KUN, PE, SZ. Equally loss. Undoubtedly errors will be made but, in the importantly, it enabled us to observe the plants in their absence of evidence to support a contrary treatment, we native habitats Nomenclatural information developed prefer to recognize as species taxa that exhibit slight but from our work has been shared with Dr. R.J. Soreng consistent morphological differences and distinct who has made it available via TROPICOS (2016). geographic distributions. This paper reflects the acquisition of new data on the rare and little studied RESULTS AND DISCUSSION dwarf species of sect. Stenopoa from the eastern Himalayas. As a result of our studies, we favor recognition of The “Flora of China” project was an important stage more taxa at the species level than in the Flora of China in the study of the Asian flora. In it, a polytypic species but group them in three species aggregates, those concept was accepted. Groups of morphologically named for P. attenuata, P. glauca, and P. albertii. The similar but ecologically or geographically isolated plants involved are all cryophytic and xerophytic populations were treated as subspecies; those without members of Stenopoa that grow in the upper mountain such isolation were treated as forms. This created a and alpine belts of non-tropical Asia, including the problem for the treatment of hybrid taxa. If the Pan-Himalayas. They are small plants, 5–15(25) cm tall, characters of one putative parental species dominated in usually with more or less rigid, folded leaf blades that a population,