Research Article |
Corresponding author: Xian-Chun Zhang ( zhangxc@ibcas.ac.cn ) Academic editor: Petra De Block
© 2021 Er-Feng Huang, Gang Yao, Ri-Hong Jiang, Lei-Lei Yang, Wang Xi, Zhong-Shuai Zhang, Xian-Chun Zhang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Huang E-F, Yao G, Jiang R-H, Yang L-L, Wang X, Zhang Z-S, Zhang X-C (2021) Hoya pyrifolia (Apocynaceae), a new species from south-western Yunnan, China. PhytoKeys 174: 95-106. https://doi.org/10.3897/phytokeys.174.60137
|
Hoya pyrifolia, a new species of Apocynaceae from Yunnan Province, China, is described and illustrated. Results from phylogenetic analyses, based on combined DNA fragments of the nuclear ribosomal external transcribed spacer (ETS), intergeneric transcribed spacer (ITS) and three plastid DNA fragments (matK, psbA-trnH and trnT-trnL), showed that the new species was nested within a clade, including Hoya species distributed in the subtropical foothills of the Himalayas and the Tibet-Sichuan Plateau. Morphologically, the new species can be distinguished from its close relatives by its pyriform and slightly pubescent leaves, as well as the 4-flowered inflorescences.
Apocynaceae, Asclepiodoideae, China, Hoya, taxonomy
Hoya R.Br., the wax plants, is a large genus circumscribed within the tribe Marsdenieae, subfamily Asclepiodoideae of Apocynaceae (
During a field investigation in Yingjiang Hsien, Yunnan Province, China, in the summer of 2018, one of the authors (E.F. Huang) discovered one population of a Hoya species, which obviously is different from congeneric taxa recorded in China and adjacent countries. Later, a specimen representing the same species was collected again from another locality (viz. Longling Hsien) in south-western Yunnan. Detailed morphological comparison and specimen examination for all the Hoya species recorded in China and adjacent regions showed that the species is new to science, thus it is formally described and illustrated here as a new species. The phylogenetic position of the new species is studied based on analyses of a combined matrix including five DNA fragments from both plastid and nuclear genomes.
Specimens of Hoya deposited in the herbaria CDBI, GH, HNWP, IBSC, KUN, P and PE were studied carefully in the present study. Field investigations of Chinese Hoya species were also conducted in recent years. Morphological characters of leaves, inflorescences and flowers of relevant species were photographed and measured. Herbarium abbreviations cited in the present study follow the Index Herbariorum (
To study the phylogenetic position of the new species within the genus Hoya, a phylogenetic study of the genus was performed, based on combined DNA fragments of the nuclear ribosomal external transcribed spacer (ETS), intergeneric transcribed spacer (ITS) and three plastid DNA regions (matK, psbA-trnH and trnT-trnL), following
Sequences were aligned using MAFFT 7.221 (
The cpDNA dataset, the nrDNA dataset and the combined dataset contained 2482, 1393 and 3875 characters, respectively. Some major clades within the genus Hoya were recovered in the BI and ML analyses of the three datasets (Figures
Maximum Likelihood (ML) tree of Hoya species inferred from the nrDNA (a including ETS and ITS) and cpDNA (b including matK, psbA-trnH and trnT-trnL) datasets. Bootstrap (BS) values ≥ 50% in ML analysis and posterior probability (PP) ≥ 0.50 in Bayesian Inference (BI) are indicated on the left and right of slanting bars above a phylogenetic node, respectively. Dashes denote that the phylogenetic node was not supported, the BS value is < 50% in the ML analysis or PP < 0.50 in the BI analysis.
Results from both BI and ML analyses of the three major datasets all showed that the new species studied here formed a clade (marked in blue in Figures
Maximum Likelihood (ML) tree of Hoya species inferred from the combined dataset of five DNA regions (ETS, ITS, matK, psbA-trnH and trnT-trnL). Bootstrap (BS) values ≥ 50% in ML analysis and posterior probability (PP) ≥ 0.50 in Bayesian Inference (BI) are indicated on the left and right of slanting bars above a phylogenetic node, respectively. Dashes denote that the phylogenetic node was not supported, the BS value is < 50% in the ML analysis or PP < 0.50 in the BI analysis.
Morphologically, the new species is similar to H. engleriana and H. longicalyx. However, it can be easily distinguished from the latter two species by a series of morphological traits (Figures
The new species is also similar to H. dickasoniana P.T.Li and H. kingdonwardii P.T.Li in morphology. The two latter species were described from Myanmar, but are not included in the phylogenetic analyses due to lack of DNA material. According to the protologues and holotypes of these two Burmese endemic species, the new species studied here can be distinguished from them by its opposite leaf arrangement, pyriform and slightly pubescent leaves (Figure
Detailed information about the morphological comparison between the new species and its close relatives are given in Table
Morphological comparison between Hoya pyrifolia E.F.Huang, its closest relatives and morphologically-similar species.
Taxa | Leaf | Inflorescence | Corona | Calyx lobes | Pollinia |
---|---|---|---|---|---|
H. chinghungensis | Ovate to broadly ovate, 10–13 mm × 7–10 mm; pubescent on both surfaces when young; base rounded to truncate, apex rounded to obtuse or acuminate; midvein evident on both surfaces | 4–5-flowered; peduncle ca. 8 mm long | Rose-colored | 1.5–2 mm long | Unknown |
H. dickasoniana | Elliptic or ovate, 9–19 mm × 5–10 mm; glabrous; base broadly cuneate to rounded, apex obtuse; midvein evident on both surfaces | 3–6-flowered peduncle ca. 5 mm long | Unknown | 2–2.5 mm long | Oblong; ca. 1 mm long; |
H. engleriana | Narrowly oblong, 20–25 mm × ca. 5 mm; pubescent on both surfaces when young; base cuneate, apex usually obtuse with mucro; midvein evident abaxially | 5–7-flowered; peduncle ca. 6 mm | Rose-colored | 1.5–2 mm long | Unknown |
H. kingdonwardii | Elliptic to slightly elliptic-lanceolate, 10–17 mm × 5–10 mm; glabrous; base cuneate and apex acuminate; midvein evident on both surfaces | 3–4-flowered; peduncle 7–10 mm long | Unknown | ca. 3 mm long | Oblong; ca. 0.8 mm long |
H. lanceolata | Lanceolate, ca. 25 mm × 15 mm; based cuneate to narrowly cuneate, apex acuminate; sparsely pubescent on both surfaces when young; midvein evident on both surfaces; | 7–12-flowered; peduncle ca. 12 mm | Rose-colored | Unknown | Unknown |
H. longicalyx | Ovate-lanceolate, 15–20 mm × ca. 10 mm; base rounded, apex acuminate; slightly pubescent; midvein depressed adaxially, raised abaxially; | 3–4-flowered; peduncle ca. 5 mm long | Whitish | 5–7 mm long | Clavate; 0.55–0.6 mm long, narrowing towards the base; |
H. pyrifolia | Pyriform, 10–14 mm × 4–7 mm; slightly pubescent adaxially, glabrous abaxially; base obtuse or rounded, apex rounded or truncate; midvein absent adaxially, obscure abaxially | 4-flowered; peduncle 8–10 mm long | Rose-colored | ca. 4 mm long | Oblong; ca. 0.6 mm long |
The species is morphologically most similar to H. engleriana, but differs by its leaves which are pyriform and 10–14 mm long (vs. narrowly oblong and 20–25 mm long), its 4-flowered inflorescences (vs. 5–7-flowered), its calyx lobes ca. 4 mm long (vs. 1.5–2 mm long) and the triangular corolla (vs. narrowly oblong to oblong-triangular).
CHINA. Yunnan Province, Yingjiang Hsien, Sudian Village, Mulonghe River, epiphytic on trunk in mid-montane evergreen forest, 25°9'38"N, 97°53'20"N, at an elevation of 1865 m, 13 August 2019, E.F. Huang 1905009 (Holotype: PE!; isotypes: PE!).
Epiphytic shrubs. Stems up to 60 cm in length, 3–4 mm in diam., branching mainly near base, branches pubescent, internodes shorter than leaves. Leaves opposite, pyriform, 10–14 × 4–7 mm, fleshy, slightly pubescent and dark green adaxially, glabrous and greyish-green abaxially, base obtuse or rounded, apex rounded or truncate, margin entire and reflexed; mid-vein invisible adaxially, obscure abaxially, lateral veins invisible on both surfaces; petioles ca. 2 mm long. Inflorescences terminal pseudumbels, flat-topped, 4-flowered, pendent; peduncle shorter than pedicels, 8–10 mm long, light green; bracteoles 2 at each pedicel base, linear, 4 × 1 mm; pedicels 1.3–1.5 cm long, light pink to yellow-green, pubescent; calyx lobes pinkish, narrowly triangular to linear, 4 × 1 mm, margin entire; corolla white, flat to slightly incurved, 1.5–1.7 cm in diam., lobes triangular-ovate, ca. 7 mm wide, apex acute; corona rose-coloured, ca. 6 mm in diam., ca. 3 × 3 mm, scales 5, fleshy, translucent, ovate-triangular; pollinia oblong, ca. 0.6 × 0.2 mm, base and apex truncate, caudicula attached at the centre of the retinaculum. Ovaries 2, attached to each other below centre, free higher up, oblong, ca. 2 mm long, ca. 1 mm wide, yellowish-white, pubescent. Follicles linear, 10–12 cm long, pubescent. Seeds linear-oblong, ca. 2.0 × 0.2 mm, coma 2.8–3.0 cm.
The species is endemic to Gaoligong Mountain, distributed in Longling and Yingjiang Counties in Yunnan Province. It is an epiphyte on tree trunks in the mid-montane evergreen forests at an elevation from 1850 m to 2150 m.
Hoya pyrifolia is named for its pyriform leaf, which is a significant feature that can be used to distinguish the species from its close relatives.
CHINA. Yunnan Province, Longling Hsien, Gaoligongshan National Forest Park, 4°50'3"N, 98°45'48"E, at an elevation of 2146 m, 26 August 2019, E.F. Huang 201908260012 (IBSC).
The authors are grateful to the curators and staff of the herbaria CDBI, GH, HNWP, IBSC, KUN, P and PE for allowing access to high quality images of herbarium specimens, to Ms. Y.J. Chen in Hangzhou Botanical Garden for the line drawing of the new species, to L.Y. Li in Kunming Institute of Botany, Chinese Academy of Sciences, for the photographs in Figures
GenBank accession numbers for samples used in this study (—, missing data; *, newly-generated sequences). GenBank accession numbers are given for ETS, ITS, matK, psbA-trnH and trnT-trnL.
Hoya affinis Hemsl., HE794222, DQ334481, HQ327536, HQ327615, HE794732; H. albiflora Zipp. ex Blume, HE794249, DQ334493, HQ327567, HQ327647, HE794761; H. anulata Schltr., HE794280, DQ334485, HQ327584, HQ327663, HE794794; H. archboldiana C.Norman, HE794258, HQ327513, HQ327566, HQ327646, HE794770; H. ariadna Decne., HE794223, DQ334502, HQ327535, HQ327614, HE794733; H. bella Hook., HE794215, HQ327518, HQ327581, HQ327660, HE794725; H. bilobata Schltr., HE794296, HE794381, HQ327599, HQ327678, HE794811; H. bordenii Schltr., HE794344, HQ327527, HQ327607, HQ327686, HE794862; H. campanulata Blume, HE794242, HE794387, MH598655, HE794484, HE794754; H. carnosa (L.f.) R.Br., HE794320, DQ334460, HQ327586, HQ327665, HE794837; H. chinghungensis (Y.Tsiang & P.T.Li) M.G.Gilbert, P.T.Li & W.D.Stevens, MN089474, MN107851, MT300095, MK361041, MT300101; H. ciliata Elmer ex C.M.Burton, HE794224, DQ334512, HQ327537, HQ327616, HE794734; H. cinnamomifolia Hook., HE794328, HQ327510, HQ327562, HQ327642, HE794845; H. citrina Ridl., HE794329, HQ327507, HQ327558, HQ327638, HE794846; H. cominsii Hemsl., HE794356, HQ327515, HQ327577, HQ327656, HE794873; H. cumingiana Decne., HE794275, HQ32752, HQ327594, HQ327673, HE794788; H. curtisii King & Gamble, HE794279, DQ334479, HQ327608, HQ327687, HE794792; H. dennisii P.I.Forst. & Liddle, HE794252, HQ327524, HQ327543, HQ327622, HE794764; H. dimorpha F.M.Bailey, HE794259, HQ327512, HQ327565, HQ327645, HE794771; H. diptera Seem., HE794285, HQ327519, HQ327583, HQ327662, HE794798; H. edeni King ex Hook.f., HE794216, DQ334476, HQ327582, HQ327661, HE794726; H. engleriana Hosseus, MT300093, MG649233, MT300096, —, MT300102; H. erythrostemma Kerr, HE794325, HQ327511, HQ327563, HQ327643, HE794842; H. finlaysonii Wight, HE794333, HQ327506, HQ327557, HQ327637, HE794850; H. heuschkeliana Kloppenb., HE794299, DQ334416, HQ327542, HQ327621, E794780; H. imbricata Decne., HE794314, DQ334480, HQ327605, HQ327684, HE794831; H. ischnopus Schltr., HE794260, HE794411, MH598707, HE794507, HE794772; H. kentiana C.M.Burton, HE794300, DQ334424, HQ327598, HQ327677, HE794815; H. kerrii Craib, HE794318, DQ334458, HQ327545, HQ327624, HE794835; H. lacunosa Blume, HE794310, DQ334499, HQ327601, HQ327680, HE794827; H. lanceolata Wall. ex D.Don, MT300094, —, MT300097, MT300099, MT300103; H. linearis Wall. ex D.Don, HE794218, HQ327517, MH598727, HQ327659, HE794728; H. lobbii Hook.f., HE794365, HE794420, MH598726, HE794516, HE794882; H. longicalyx Wang Hui & E.F.Huang, MN268319, MN116005, MT300098, MT300100, MT300104; H. macgillivrayi F.M.Bailey, HE794262, DQ334488, HQ327568, HQ327648, HE794774; H. meliflua Merr., HE794315, DQ334429, HQ327571, HQ327651, HE794832; H. merrillii Schltr., HE794349, HQ327505, HQ327555, HQ327635, HE794866; H. mitrata Kerr, HE794309, DQ334500, HQ327604, HQ327683, HE794826; H. multiflora Blume, HE794238, DQ334487, HQ327550, HQ327629, HE794750; H. naumannii Schltr., HE794265, HE794434, MH598742, HE794529, HE794777; H. odorata Schltr., HE794277, HQ327504, HQ327554, HQ327634, HE794790; H. onychoides P.I.Forst., Liddle & I.Liddle, HE794248, HE794439, MH598748, HE794533, HE794760; H. patella Schltr., HE794255, DQ334498, HQ327553, HQ327633, HE794767; H. polyneura Hook.f., HE794366, HQ327509, HQ327560, HQ327640, HE794883; H. praetorii Miq., HE794237, HQ327520, HQ327585, HQ327664, HE794749; H. puber Blume, HE794287, HQ327526, HQ327544, HQ327623, HE794800; H. pubicalyx Merr., HE794321, DQ334447, HQ327588, HQ327666, HE794838; H. pyrifolia E.F.Huang, MW066464*, MW035791*, MW066465*, MW066466*, MW066467*; H. retusa Dalzell, HE794364, DQ334457, MH598775, HQ327632, HE794881; H. rubida Schltr., HE794266, HE794453, MH598777, HE794545, HE794778; H. serpens Hook.f., HE794368 DQ334482, HQ327575, HQ327654, HE794885; H. siariae Kloppenb., HE794355, HE794459, JX120795, HE799701, HE794870; H. sussuela Merr., HE794233, HE794464, MH598784, HE794559, HE794743; H. telosmoides Omlor, HE794240, DQ334486, HQ327592, HQ327671, HE794752; H. thailandica Thaithong, HE794219, HE794466, —, HE794561, HE794729; H. thomsonii Hook.f., HE794369, HQ327502, HQ327546, HQ327625, HE794886; H. vitellina Blume, HE794342, HQ327508, HQ327559, HQ327639, HE794859; H. waymaniae Kloppenb., HE794244, HQ327522, HQ327596, HQ327675, HE794756; Marsdenia laxiflora Donn.Sm., MK214583, LR794776, MH748870, —, LR794694.