Aristolochia sinoburmanica (Aristolochiaceae), a new species from north Myanmar

Abstract Aristolochia sinoburmanica Y.H.Tan & B.Yang, a new species of Aristolochiaceae from Putao, Kachin State, Myanmar, is described and illustrated. According to morphology (strongly curved perianth, 3-lobed limb, as well as 3-lobed gynostemium, anthers 6, adnate in 3 pairs to the base of gynostemium, opposite to the lobes), the species belongs to Aristolochia subgenus Siphisia. It is morphologically similar to A. faviogonzalezii, A. hainanensis, A. tonkinensis, A. saccata and A. xuanlienensis. The major differences between them are outlined and discussed. A detailed description, along with line drawings, photographs, habitat, distribution and conservation status, as well as a comparison to morphologically similar species, are also provided.


Introduction
Aristolochia L., with about 550 recognised species (González 2012), is a predominantly tropical and subtropical genus that extends to the Mediterranean and temperate zones worldwide and has highest species richness in the New World (Wanke et al. 2006). The genus is also rich in Asia, particularly in eastern and southern Asia, with more than 70 species (Ma 1989;Do et al. 2015a). There are currently 61 species recorded in China (Zhu et al. 2016(Zhu et al. , 2017, 22 species in Vietnam (Do and Nghiem 2017) and 12 species in Myanmar (Kress et al. 2003). Recent phylogenetic studies of the genus based on morphological and molecular data suggested the subdivision of Aristolochia into three subgenera, i.e. subgenus Aristolochia, subgenus Siphisia and subgenus Pararistolochia (Wanke et al. 2006). The distribution and key morphological characters of the subgenus Siphisia have been described and discussed by González et al. (2014) and Do et al. (2015aDo et al. ( , 2015b. During a field expedition to Putao, Kachin state, north Myanmar, an unknown species of Aristolochia was collected. After careful studies of the genus, particularly the floral characteristics of those species in the adjacent regions, as well as comparison between this unknown species and its related species, it is confirmed as a new species of Aristolochia which has strongly curved perianth, 3-lobed limb, as well as 3-lobed gynostemium and should be assigned to the subgenus Siphisia. The new species presented here was also collected by a famous Chinese botanist, Professor K. M. Feng in 1959 (KUN, No. 0163232) from northwest Yunnan, China. The specimen consists of four leaves, being complemented by good field notes and was identified as Aristolochia hainanensis. In this paper, this new Aristolochia species is described and illustrated.

Material and methods
Measurements and morphological character assessments of the possible new species Aristolochia sinoburmanica were made from both dried specimens and field observations of living plants which allowed comparison of morphological characters and colouration of the perianth (utricle, tube and limb) as well as morphology of the inside of the trap flowers, including the gynostemium, which are often impossible to observe in dried specimens. The description of the new species follows the terminology used by Hwang et al. (2003) and Do et al. (2015a). This new species was compared with the morphologically similar species A. hainanensis Merrill, A. saccata Wallich and also the recently published new species A. xuanlienensis (Huong et al. 2014 (Do et al.2015a), according to the descriptions from type specimens and dried herbarium specimens and also literature descriptions (Hwang1988, Hwang et al. 2003, Huong et al. 2014, Ma 1989, Do et al. 2015a, 2015b. Protologues and images of type specimens and dried herbarium specimens were gathered from JSTOR Global Plants (http://plants.jstor.org) and the KUN website (http://db.kun.ac.cn/).

Data resources
The data underpinning the analyses reported in this paper are deposited in the Dryad Data Repository at https://doi.org/10.5061/dryad.2501p.  (Do et al. 2015a), but is distinguishable from these species by the following diagnostic characters: leaf blade ovate or ovate-lanceolate to narrowly ovate, subcoriaceous, base rounded to slightly cordate; cyme solitary on old woody stems and young branches, each cyme with 1-2 flowers; perianth claret (deep purple red), outside densely brown hirsute with parallel dark purple veins, 6.5-7.5 cm high; tube horseshoe-shaped, 8.3-8.5 cm, uniformly claret (deep purple red), with visible dark purple veins, limb trumpet-shaped, 4.2-4.8 cm high, 4-4.4 cm wide, 3-lobed, lobes subequal; throat deep purple red, glabrous. The summary and main characters comparison is presented in Table 1.
Etymology. The species epithet refers to the type locality in Myanmar and adjacent regions of China. It also shows that the two countries are friendly neighbours, their friendship being retained over a long period and also expresses our appreciation for the whole-hearted cooperation amongst members of the China-Myanmar joint expedition.
Distribution and habitat. Aristolochia sinoburmanica is hitherto known from the type locality of Putao, Kachin state in north Myanmar and adjacent regions of Gongshan County, northwest Yunnan, southwest China, where, according to one sheet of the specimen deposited in KUN, it is a perennial liana which grows under the montane broadleaf forests, at an elevation of ca. 900-1400 m.
Preliminary conservation status. In Nov. 2014, the China-Myanmar joint expedition conducted the first field investigation of plant diversity along the same route in north Myanmar, within the area which included the type locality of this new species. The path through the mountains could only be accessed by foot, but in the most recent expedition in May 2017, with the development of road construction, most of the trees and habitats have been destroyed. A. sinoburmanica is known from a single population on the roadside. In fact, during the present study, only two healthy individuals were located growing about 20m apart from each other. Therefore, the new species is assigned a preliminary status of vulnerable (VU) according to the IUCN Red List Categories (IUCN 2012). However, since very few details exist about its natural distribution, a detailed investigation of the same habitats may identify more populations and individuals of this new species. The lack of sufficient data currently does not allow a final risk evaluation and the species might be regarded as data deficient (DD). Further field surveys in northern Myanmar are needed to gain more information on its distribution.
Additional specimens examined. China. Yunnan: Gongshan, east of Dulong River, 27°41'51.81"N, 98°19'11.22"E, 1400m a.s.l., 12 Nov. 1959.  Table 1). A. sinoburmanica, with a horseshoe-shaped perianth of 3 lobes which are valvate in preanthesis, annulated perianth throat and gynostemium with trilobed stigma on top, each lobe consisting of one pair of stamens, belongs to the Aristolochia subgenus Siphisia (Wanke et al. 2006, Do et al. 2015a).This new discovery, along with several new species recently described from Vietnam (Huong et al. 2014, Do et al. 2014, 2015a, 2015b, Guangxi and Hainan Island, China (Xu et al. 2011, Huang et al. 2013, Wu et al. 2013 and Peninsular Malaysia (Yao 2012), provide evidence that the genus Aristolochia and, in particular, Aristolochia subgenus Siphisia is very diverse in South-East Asia. Currently there are only 12 Aristolochia species recorded in Myanmar (Kress et al. 2003), indicating that the species diversity of Aristolochia in Myanmar is still open to discovery. It is predicted that more new species will be discovered when more field investigations are conducted in this region. and constructive suggestions, which help to improve the quality of this manuscript. We thank Zhengmeng Yang for the illustration. This work was financially supported by a project of the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Grant No.Y4ZK111B01).