2022, Vol. 30
The genus Didymoplexis Griff., was founded by Griffith in 1844. Approximately 21 species are distributed in India, South China, Indochina to Ryukyu Islands and the Philippines, the Malay Archipelago to Papua New Guinea, tropical Australia, and the southwest Pacific islands, also in southwest Africa and Madagascar[1-2]. Three species were previously reported in China: D. vietnamica, D. pallens, D. micradenia, which are mainly distributed in Hainan, Taiwan, Guangxi and Guangdong[3].
In Hainan Island, mild climate and diverse vegetation types[4] provide a habitat for a large number of tropical plants, among which orchids are parti- cularly typical. In recent years, there have been many reports on discovery of orchids[5-8]. During a recent botanical survey in Huishan Nature Reserve (Qiong- hai), a species of the genus Didymoplexis Griff. was discovered. After dissection and study of fresh materials and literature review[9-12], it was identified as a newly recorded species in China, Didymoplexis striata. This species was previously recorded in Malaysia, Brunei, Indonesia, Solomon Islands, Thai- land, and other regions[2, 11]. The discovery of the species in Hainan Island showed a closer historical relationship of Hainan Island with Southeast Asia[13]. Didymoplexis striata is morphologically similar to D. pallens, except that it has a longitudinally striate perianth tube and an entire lip with a pale yellowish median thickening band.
Didymoplexis striata J.J. Sm., Icon. Bogor. [Boer-lage] 2: t. 104 B (1903). (条纹双唇兰) Fig. 1
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Fig. 1 Didymoplexis striata J.J. Sm. A: Habitat; B: Flowering plant; C: Flower, Lip, Column. (Photoed by Kai Zhang) |
Holomycotrophic plants. Plants 10-20 cm tall. Rhizome pale brown, fusiform or moniliform, 8-15 mm×5-8 mm; roots few to many, wiry, often with small globose thickenings. Peduncle 5-18 cm, with 3-5 scalelike sheaths, pale brown to reddish-brown. Pedicel 0.5-3 cm, elongating in fruit, laxly to sub- densely 2-5-flowered; floral bracts triangular cupped, ca. 2 mm, apex acute. Flowers opening in succession, white, campanulate; pedicel and ovary erect, brown, 0.7-1.2 cm; pedicel extending to 15 cm in fruit. Dorsal sepal and petals 4-7 mm, usually united for more than 1/2 of their length, free portion ovate-triangular, shallowly 3-lobed, each lobe ovate-deltoid and with an obtuse apex; lateral sepals 3-4.5 mm, connate with each other for up to 1/2 of their length, and with petals for 1/3 of their length, free portion 2-lobed, each lobe ovate and with an obtuse apex, reflexed; with 3 brown stripes on sepals and 2 brown stripes on petals; lip saddle-shaped, 4.5-6 mm×6-7 mm, erose-crenate, lateral margins erect or incurved, apex subtruncate; disk with a pale yellowish median thickening band. Column slightly curved, clavate, ca. 4 mm, apex dilated and with 2 conical wings; column foot slightly curved, 2-3 mm. Fl. Apr.—May, Fr. May—Jun.
Specimen: Qionghai (琼海): Huishan Provincial Nature Reserve, Hainan Province. April 24, 2021, Zhang Peichun 2021001 (HUTB).
Distribution: Malaysia, Brunei, Indonesia (Java and Borneo) and the Solomon Islands (New Georgia and Krombangala), Thailand. Qionghai (琼海), Hai- nan Province, China.
Ecology: Closed lowland rain forests with abundant litter, 300-600 m a.s.l. Flowering was observed in April and May.
Protection Status: This species has a very narrow distribution in Huishan Provincial Nature Reserve, Hainan Province. At present, only one population has been found, and the number of individuals is 15. According to the evaluation criteria of the threatened degree of species by the World Conservation Union[14], We speculated that the species is a critically endangered species based on the following points (CR: C2ai): the estimated population number of mature individuals is less than 250 (Cr: C), and it is estimated that there is no subpopulation with more than 50 mature individuals (Cr: C2ai). It is a species with a very small population due to its harsh growth conditions and susceptibility to damage. Follow-up observation of the population dynamics of the newly recorded species and related studies of pollination and reproductive biology should help to develop effective conservation measures.
To facilitate the identification of Didymoplexis species, we compiled an identification key to the 4 species distributed in China.
A taxonomic key to the four species in the genus Didymoplexis Griff. in China
1. Column foot conspicuous, longer than 1 mm; lip 6-7 mm wide, broader than long.
2. Bracts triangular, cup-shaped, lip with appendages························································ D. vietnamica Ormd.(中越双唇兰)
2. Bracts ovate, lip without appendages.
3. Lip disk with a dense row of warty papillae along midvein························································· D. pallens Griff. (双唇兰)
3. Lip disk with a pale yellowish median thickening band····················································· D. striata J.J. Sm. (条纹双唇兰)
1. Column foot inconspicuous, less than 1 mm, lip 4-5 mm wide······························· D. micradenia (Rchb.f.) Hemsl. (小双唇兰)
Acknowledgment Thanks to our partners of the research group for their help, to the staff of Huishan Provincial Nature Reserve for their cooperation in the survey, and to Dr. Kai Zhang for providing valuable photos and sharing his opinions.
| [1] |
CHEN S C, GALE S W, CRIBB P J. Didymoplexis[M]//WU Z Y, RAVEN P H, HONG D Y. Flora of China, Vol. 25. Beijing: Science Press & St. Louis: Missouri Botanical Garden Press, 2009: 205-206.
|
| [2] |
GOVAERTS R, DRANSFIELD J, ZONA S, et al. World Checklist of Didymoplexis[OL]. (2021-05-17) http://wcsp.science.kew.org/.
|
| [3] |
CHEN X Q, WOOD J J. Ornithochiluse[M]//WU Z Y, RAVEN P H, HONG D Y. Flora of China, Vol. 25. Beijing: Science Press & St. Louis: Missouri Botanical Garden Press, 2009: 466.
|
| [4] |
YANG X B, CHEN Z Z, LI D H, et al. Vegegraphy of Hainan, V1[M]. Beijing: Science Press, 2019: 144-153. (in Chinese).
|
| [5] |
LU G, HU A Q, XIAO Y, et al. Gastrodia punctata Aver., a newly recorded species of Orchidaceae from China[J]. Guihaia, 2017, 37(2): 228-230. (in Chinese). DOI:10.11931/guihaia.gxzw201507013 |
| [6] |
HUANG M Z, WANG Q L, YANG G S. Two genera and seven species of Orchidaceae, newly recorded in Hainan[J]. Chin J Trop Crops, 2017, 38(1): 1-3. (in Chinese). DOI:10.3969/j.issn.1000-2561.2017.01.001 |
| [7] |
YE K. Newly recorded species of Orchidaceae in Hainan, China[J]. Chin J Trop Crops, 2019, 40(11): 2261-2263. (in Chinese). DOI:10.3969/j.issn.1000-2561.2019.11.022 |
| [8] |
HUANG M Z, WANG Y, WANG Q L, et al. Miscellaneous notes on Orchidaceae from Hainan (Ⅲ)[J]. Chin J Trop Crops, 2021, 42(3): 703-706. (in Chinese). DOI:10.3969/j.issn.1000-2561.2021.03.013 |
| [9] |
HUANG Y S, LU M X, YANG J C, et al. Didymoplexis vietnamica, A newly recorded species of Didymoplexis (Orchidaceae) from China[J]. Guihaia, 2011, 31(5): 578-580. (in Chinese). DOI:10.3969/j.issn.1000-3142.2011.05.004 |
| [10] |
TIAN H Z, DONG Q Y, LI X L. Five new records of Orchidaceae from Hainan, China[J]. Chin J Trop Crops, 2012, 33(11): 1926-1929. DOI:10.3969/j.issn.1000-2561.2012.11.002 |
| [11] |
HSU T C, YANG T Y, PITISOPA F, et al. New records and name changes for the orchids in the Solomon Islands[J]. Taiwania, 2016, 61(1): 21-26. DOI:10.6165/tai.2016.61.21 |
| [12] |
LIU Y R, GUO J Q, LIU Z C, et al. New records of Orchidaceae from Guangdong Province[J]. Subtrop Plant Sci, 2020, 49(1): 65-68. (in Chinese). DOI:10.3969/j.issn.1009-7791.2020.01.011 |
| [13] |
YU W G, JIN Z Q, LUO Y B, et al. Analysis of floristic composition and characteristics of wild orchids in Hainan Island[J]. Chin J Trop Crops, 2007, 28(2): 108-114. (in Chinese). DOI:10.3969/j.issn.1000-2561.2007.02.022 |
| [14] |
IUCN. IUCN red list categories and criteria, er. 3.1[R]. 2nd ed. Species Survival Commission. Gland, Switzerland, Cambridge, UK: IUCN, 2012: 16-18.
|