Research Article |
Corresponding author: Yun-Hong Tan ( tyh@xtbg.org.cn ) Academic editor: Wen-Bin Yu
© 2019 Cheng Liu, Ji-Dong Ya, Yun-Hong Tan, Hua-Jie He, Gui-Jun Dong, De-Zhu Li.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Liu C, Ya J-D, Tan Y-H, He H-J, Dong G-J, Li D-Z (2019) Marsdenia yarlungzangboensis (Apocynaceae, Asclepiadoideae), a new species from Xizang, China. In: Cai J, Yu W-B, Zhang T, Li D-Z (Eds) Revealing of the plant diversity in China’s biodiversity hotspots. PhytoKeys 130: 85-92. https://doi.org/10.3897/phytokeys.130.34152
|
Marsdenia yarlungzangboensis (Apocynaceae, Asclepiadoideae), a new species from Motuo County, southeastern Xizang of China, is described and illustrated. It is morphologically similar to M. medogensis, M. tenii and M. yuei, the major differences between the new species and the morphological relatives are outlined and discussed. A diagnostic key to the new species and its closely related species in China is provided.
Marsdenia, Marsdenia yarlungzangboensis, new species, China
Marsdenia R.
In 2016, we collected an unknown species of Apocynaceae during fieldwork in Motuo County, southeastern Xizang, China. This species was identified as a member of Marsdenia by characterizing woody vines with umbelliform inflorescences, campanulate corollas with fleshy corona attached to gynostegium and the erect pollinia attached to the caudicles at the base (
Vouchers of Marsdenia yarlungzangboensis were collected from Motuo County, Xizang of China. The photographs and phenology data were obtained during the field expeditions.
Morphological observations and measurements of the new species were carried out based on living plants and dry specimens. The morphology of opened corolla, opened calyx, gynostegium and staminal corona, pistil, pollinarium were observed by using a Keyence VHX-700F Digital Microscope (Keyence, Osaka, Japan) and based on dry specimens. All morphological characters are described according to the terminology presented by
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.
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!)
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 × 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 × 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 × 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.
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).
Flowering from November to December.
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.
The specific epithet ‘yarlungzangboensis’ is derived from the type locality, Yarlung Zangbo Grand Canyon, Motuo County, southeast Xizang, China.
Yǎ Lǔ Zàng Bù Niú Nǎi Cài (Chinese pronunciation); 雅鲁藏布牛奶菜 (Chinese name).
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. (
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 × 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 × 2–3 cm, base rounded, lateral veins 7 or 8 pairs | petiole to 4 cm; blades oblong-ovate, to 12.5 × 7.5 cm, base cordate, lateral veins ca. 5 pairs; | petiole ca. 4 cm; blades ovate, ca. 9.5 × 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 × 3–4 mm, basal glands 5 | ovate, ca. 4 × 2 mm | elliptic, ca. 3 × 2 cm | rounded, ca. 3 × 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 × 3–4 mm, apex emarginate, margin reddish and ciliate | white, 1.5–2 cm in diam., throat glabrous; lodes broadly ovate, ca. 9 × 9 mm, apex rounded | yellowish white, ca. 6 mm, throat pilose with retrorse hairs, lobes ca. 3.5 × 2.5 mm, lobes densely appressed tomentose in center | white, glabrous except for sparsely ciliate margin, lobes oblong-obovate, ca. 5.5 × 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.
1a | Corolla tube longer than lobes | M. sinensis |
1b | Corolla tube shorter than lobes | 2 |
2a | Corolla lobes 9–12 mm | 3 |
3a | Leaf blade 5.5–10 cm wide; inflorescences 7–15 cm; corolla interior pubescent; sepals ca. 8 × 6 mm | M. koi |
3b | Leaf blade 2–3 cm wide; inflorescences 4–4.5 cm; corolla glabrous; sepals 3–4 × 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 |
We are grateful to Chang-Hong Li, Hai-ping Wei, Ma Ni, Duo-Jie Sanjie for their kind help in the fieldwork; to Lian-Yi Li for taking morphological photographs of opened corolla, opened calyx, gynostegium and staminal corona, pistil, pollinarium by Keyence VHX-700F Digital Microscope (Keyence, Osaka, Japan); and to Ling Wang for the line drawing. This research was supported by the programme of Germplasm Bank of Wild Species, National Science & Technology Infrastructure and the Large-scale Scientific Facilities of the Chinese Academy of Sciences (2017-LSFGBOWS-02).