Marsdenia yarlungzangboensis (Apocynaceae, Asclepiadoideae), a new species from Xizang, China Author Liu, Cheng Author Ya, Ji-Dong Author Tan, Yun-Hong Author He, Hua-Jie Author Dong, Gui-Jun Author Li, De-Zhu text PhytoKeys 2019 130 85 92 http://dx.doi.org/10.3897/phytokeys.130.34152 journal article http://dx.doi.org/10.3897/phytokeys.130.34152 1314-2003-130-85 D5FD2CEFE7695B6794280077CFB5691F 3387840 Marsdenia yarlungzangboensis C.Liu, J.D.Ya & Y.H.Tan sp. nov. Figs 1 , 2 Diagnosis. Marsdenia yarlungzangboensis is morphologically similar to M. medogensis , M. tenii and M. yuei , but differs from M. medogensis in inflorescences pubescent; sepals suborbicular; corolla yellow, throat red and densely pilose, shorter lobes and reddish outside , apex emarginate, margin reddish and ciliate; corona lobes triangular, to base of anthers; stigma head hemispherical; and differs from M. tenii in leaf blades elliptic; sepals suborbicular; corolla yellow, throat red, lobes reddish outside, margin reddish; stigma head hemispherical, conspicuously exserted from anther appendages and corolla tube; and also differs from M. yuei in leaf blades elliptic; inflorescences unbranched and pubescent; sepals suborbicular; corolla yellow, throat red and densely pilose; lobes ovate, apex emarginate; corona lobes to base of anthers. Type. CHINA. Xizang: Motuo County, Renqinbeng, on margins of the subtropical evergreen broad-leaved forest, 29°20'08.59"N , 95°21'38.42"E , 1848 m a.s.l., 15 Nov 2016, in flowering, C. Liu, J.D. Ya, H.J. He & C.H. Li 16CS11914 (holotype: KUN!, isotype: KUN!) Description. Lianas woody, up to 10 m. Stems pale gray, sap white. Branchlets glabrous or distal parts minutely puberulent. Leaves opposite, petiole 1.5-2.5 cm, puberulent; blades elliptic, 7-12 x 3.5-6 cm, papery, glabrescent or sparsely hairy and denser along veins adaxially, base rounded or shallowly cordate, apex acuminate, margin entire, revolute, abaxially pale; lateral veins 4 or 5 pairs. Inflorescences umbel-like or with several umbel-like cymules along unbranched rachis, 3-7 cm, rachis at least 1.5 cm; peduncle 1.5-6 cm, pubescent; pedicel 5-7 mm, pubescent. Sepals suborbicular, pubescent outside, ca. 4 x 3-4 mm, ciliate, basal glands 5. Corolla yellow, campanulate, 1-1.5 cm in diam., glabrous outside, pubescent inside; tube ca. 5 mm, glabrous outside; throat red and densely pilose; lobes ovate and reddish outside, twisted to the right, 5-6 x 3-4 mm, apex emarginate, margin reddish and ciliate. Corona lobes triangular, fleshy, to base of anthers, almost flat. Anther appendages oblong, apex membranous; Pollinia 2 per pollinarium, erect, reniform. Ovary glabrous, ca. 2 mm, 2-carpelled, free. Stigma head hemispherical, conspicuously exserted from anther appendages and corolla tube. Follicles and seeds not seen. Figure 1. Marsdenia yarlungzangboensis C.Liu, J.D.Ya & Y.H.Tan A habit B flower (lateral view) C opened calyx D opened corolla E gynostegium and staminal corona F pistil G pollinarium. Figure 2. Marsdenia yarlungzangboensis C.Liu, J.D.Ya & Y.H.Tan A habit B inflorescences and adaxial leaf surface C abaxial leaf surface D flower (lateral view) E flower (front view, showing hairy throat) F opened corolla G opened calyx H gynostegium and staminal corona I pistil J pollinarium. Photo credit: Cheng Liu ( A-E ) and Lian-Yi Li ( F-J ). Phenology. Flowering from November to December. Distribution and habitat. Marsdenia yarlungzangboensis grows at the margins of subtropical evergreen broad-leaved forest with main community types of Castanopsis echinocarpa J. D. Hooker & Thomson ex Miquel and Quercus gambleana A. Camus, Renqinbeng, Motuo County, Xizang, China, at an elevation of 1800-2100 m. Etymology. The specific epithet ' yarlungzangboensis ' is derived from the type locality, Yarlung Zangbo Grand Canyon, Motuo County, southeast Xizang, China. Vernacular name. Yǎ Lǔ Zang Bu Niu Nǎi Cai (Chinese pronunciation); 雅鲁藏布牛奶菜 (Chinese name). Discussion. Based on the larger gynandrium, corolla tube almost equal in length to gynostegium and with umbel-like cymules along unbranched rachis, Marsdenia yarlungzangboensis belongs to Marsdenia sect. Ruehssia (Karst.) Fourn. ( Tsiang and Li 1977 ). Morphologically, it is similar to M. medogensis , M. tenii and M. yuei in terms of habit and floral morphology, but can be distinguished from M. medogensis in inflorescences pubescent (vs. glabrous); sepals suborbicular (vs. ovate); corolla yellow (vs. white), throat red and pilose (vs. glabrous), apex emarginate (vs. rounded), margin reddish and ciliate; corona lobes triangular (vs. oblong), to base of anthers (vs. as long as anther appendages); stigma head hemispherical (vs. discoid, convex). It also differs from M. tenii in its stems glabrous or distal parts minutely puberulent (vs. densely yellow-brown tomentose); leaf blades elliptic (vs. oblong-ovate); sepals suborbicular (vs. elliptic); corolla yellow, throat red and pilose, lobes reddish outside (vs. yellowish white, throat pilose with retrorse hairs); stigma head hemispherical (vs. 2-cleft, conical), conspicuously exserted from anther appendages and corolla tube (vs. equalling anther appendages). Beyond that, it can be distinguished from M. yuei in leaf blades elliptic (vs. ovate); inflorescences unbranched, pubescent (vs. branched, glabrous); sepals suborbicular (vs. rounded); corolla yellow (vs. white), throat red and densely pilose (vs. glabrous); lobes ovate, apex emarginated (vs. oblong-obovate, apex rounded); corona lobes to base of anthers (vs. as long as anther appendages). The detailed characters amongst the three related species are provided in Table 1 . Table 1. Diagnostic character differences amongst Marsdenia yarlungzangboensis , M. medogensis , M. tenii and M. yuei.

Character	M. yarlungzangboensis	M. medogensis	M. tenii	M. yuei
Stems	stems pale gray, glabrous or distal parts minutely puberulent	stems pale gray, nodes pilose	stems densely yellow-brown tomentose	stems glabrous except for flowers
Leaves	petiole 1.5-2.5 cm; blades elliptic, 7-12 x 3.5-6 cm, base rounded or shallowly cordate, abaxially pale, lateral veins 4 or 5 pairs	petiole 1-1.6 cm; blades oblong, 10-11 x 2-3 cm, base rounded, lateral veins 7 or 8 pairs	petiole to 4 cm; blades oblong-ovate, to 12.5 x 7.5 cm, base cordate, lateral veins ca. 5 pairs;	petiole ca. 4 cm; blades ovate, ca. 9.5 x 5.8 cm, base shallowly cordate, lateral veins 4 or 5 pairs
Inflorescences	with several umbel-like cymules along unbranched rachis, pubescent; rachis to at least 1.5 cm	umbel-like, glabrous 4 -8- flowered	with several umbel-like cymules along unbranched rachis; rachis to at least 2 cm	umbel-like, up to 9-flowered
Peduncle and Pedicel	peduncle 1.5-6 cm, pedicel 5-7 mm, pubescent	peduncle 4-4.5 cm, pedicel 2-2.5 cm, glabrous	peduncle to 3 cm, pedicel ca. 5 mm	peduncle ca. 1.5 cm, pedicel to 9 mm
Sepals	suborbicular, pubescent outside, ca. 4 x 3-4 mm, basal glands 5	ovate, ca. 4 x 2 mm	elliptic, ca. 3 x 2 cm	rounded, ca. 3 x 2.5 mm, finely appressed puberulent
Corolla	yellow, ca. 1-1.5 cm in diam., throat red and densely pilose; lobes ovate, ca. 5 -6 x 3 - 4 mm, apex emarginate, margin reddish and ciliate	white, 1.5-2 cm in diam., throat glabrous; lodes broadly ovate, ca. 9 x 9 mm, apex rounded	yellowish white, ca. 6 mm, throat pilose with retrorse hairs, lobes ca. 3.5 x 2.5 mm, lobes densely appressed tomentose in center	white, glabrous except for sparsely ciliate margin, lobes oblong-obovate, ca. 5.5 x 2.5-3.2 mm, apex rounded
Corona lobes	triangular, to base of anthers	oblong, as long as anther appendages	to base of anthers	narrowly triangular, as long as anther appendages
Stigma head	hemispherical, conspicuously exserted from anther appendages and corolla tube	discoid, convex, slightly exserted from anther appendages	2 -cleft, conical, equalling anther appendages	hemispherical, conspicuously exserted from anther appendages and corolla tube

According to field surveys, this new species is only found in the type locality Renqinbeng, Motuo County, Xizang. This area is one of China's biodiversity hotspots and consists of a diverse series of ecosystems from subtropical broad-leaved forests to alpine meadows above the tree line with an altitudinal range of 150-6000 m above sea level. Plant diversity is also poorly studied in this area, and some new taxa have been discovered in recent years. In order to better understand and conserve the biodiversity in this area, more extensive investigations are needed in the future. A diagnostic key to the new species and its closely related species in China

1a	Corolla tube longer than lobes	M. sinensis
1b	Corolla tube shorter than lobes	2
2 a	Corolla lobes 9-12 mm	3
3a	Leaf blade 5.5-10 cm wide; inflorescences 7-15 cm; corolla interior pubescent; sepals ca. 8 x 6 mm	M. koi
3b	Leaf blade 2-3 cm wide; inflorescences 4-4.5 cm; corolla glabrous; sepals 3-4 x 2-2.5 mm	M. medogensis
2b	Corolla lobes 3-7 mm	4
4a	Base of leaf blade rounded to truncate; inflorescences unbranched	5
5a	Plants tomentose; corolla white, 6-8 mm, stigma head 2-cleft, conical, equalling anther appendages	M. tenii
5b	Plants puberulent; corolla yellow, 1-1.5 cm, stigma head hemispherical, conspicuously exserted from anther appendages and corolla tube	M. yarlungzangboensis
4b	Base of leaf blade cordate; inflorescences usually obviously branched	6
6a	Peduncle to 16 cm; corolla interior pilose; corona lobes shorter than corolla tube	M. hainanensis
6b	Peduncle ca. 1.5 cm; corolla interior glabrous; corona lobes longer than corolla tube	M. yuei