Yushania tongpeii (Poaceae, Bambusoideae), a new bamboo species from north-eastern Yunnan, China

Abstract Yushania tongpeii D.Z.Li, Y.X.Zhang & E.D.Liu, a new species of the temperate bamboo tribe Arundinarieae (Poaceae: Bambusoideae), is described and illustrated from north-eastern Yunnan, China. Yushania tongpeii is characterised by taller branching from nodes 1–2 m above the ground, usually three branches at the node, sparse purple spots and thin white powder on the internode, densely purple-spotted culm sheaths, glabrous margins of culm sheaths and tomentose leaf ligules. Based on the morphological features, this new species is assigned to section Yushania.


Introduction
Yushania P.C. Keng, (1957) is one of the largest genera of the tribe Arundinarieae (i.e. the temperate woody bamboos) (Poaceae, Bambusoideae). It consists of more than 80 species, which are mainly distributed in the mid-elevation mountains and subalpine areas (1000-3800 m alt.) of East and Southeast Asia, with the centre of diversity situated in south-western and south-eastern China (Keng 1957, Keng and Wang 1996, Ohrnberger 1999, Li et al. 2006, Vorontsova et al. 2017, Yi et al. 2008, especially the biodiversity hotspot Mountains of Southwest China. These bamboos are dominant elements for the understorey vegetation of the forest ecosystem. More than 70 species of Yushania have been described in China (Yi et al. 2008(Yi et al. , 2017, some of which are the staple food of the giant panda (Yi and Jiang 2010).
Species of Yushania are characterised by the long-necked rhizomes, diffuse culms, one to many branches at the node, semelauctant and paniculate inflorescence and three stamens (Li et al. 2006). Most taxa of this genus were described without reproductive features due to infrequent flowering. Only 11 species have inflorescence information in Flora Reipublicae Popularis Sinicae (Keng and Wang 1996) and Flora of China (Li et al. 2006). The genus Yushania is divided into two sections, i.e. Y. sect. Brevipaniculatae T.P. Yi and Y. sect. Yushania, based mainly on the culm height and branch number at the node (Yi 1986(Yi , 1995. Sect. Brevipaniculatae is distinguished by taller culms, many and subequal branches at each node and terminal panicles or racemes; while species of sect. Yushania are usually shorter and have 1 branch at the mid-culm node or 1 branch at the lower part of the culm and 3-8 branches at the upper part of the culm and terminal panicles.
During a botanical survey to Sanjiangkou, Wumengshan National Nature Reserve, Daguan County, Yunnan, China in 2016, specimens and relevant DNA samples of several bamboo species were collected. One of them has long-necked rhizomes, usually three branches at the node and occurs at elevations around 2300 m. These characters are typical of the genus Yushania. After comparison with specimens of Yushania deposited at KUN and some literature (e.g. Keng and Wang 1996, Li et al. 2006, Yi et al. 2008, we concluded that it did not match any described species of Yushania. In order to know more about its habitat, distribution range and morphological features, we revisited Sanjiangkou, Wumengshan National Nature Reserve in September 2018 and more specimens were collected. In this paper, we described it as a new species, i.e. Yushania tongpeii D.Z.Li,Y.X.Zhang & E.D.Liu.
Phenology. New shoots May to July. Distribution and habitat. This new species is only found in Daguan County, north-eastern Yunnan, China. It occurs above the upper limit of distribution of Chimonobambusa tumidissinoda Hsueh&T.P.Yi ex Ohrnberger in this area, and grows under the evergreen broadleaved forests at an altitude between 2200-2400 m.
Etymology. The specific epithet refers to Professor Tong-Pei Yi (1933Yi ( -2016, who made great contributions to the taxonomy of the alpine bamboos (particularly in

Discussion
The vegetative characters of Yushania tongpeii, such as three branches at the upper part of the nodes and medium height culms, are similar to the species of section Yushania, particularly the three species listed in Table 1. All these three species have less than five branches at the node, white powder on the internode or below the node, prominent nodal sheath scar, falcate culm sheath auricles and white powdery petioles (except for Y. pingshanensis). However, some subtle features make Y. tongpeii distinctive, including sparse purple spots on the internode, densely purple-spotted culm sheaths, glabrous margins of culm sheaths and tomentose leaf ligules. Therefore, this new species should be assigned to section Yushania on the basis of morphology.
Some researchers analysed the diversity and the distribution patterns of endemic seed plants in China (Huang et al. 2014, Huang et al. 2016. The Central Yunnan Plateau Subregion, one of the floristic units in China (Wu et al. 2010), is one of the two centres of Chinese endemic flora (Huang et al. 2016). Wumengshan National Nature Reserve is located at the east edge of the Central Yunnan Plateau Subregion. Therefore, the discovery of Yushania tongpeii, which is endemic to Wumengshan National Nature Reserve, gives meaning for studying the diversity of endemic species in this area.