Dendrobium roseiodorum (Orchidaceae): a new species from Vietnam

RESEARCH ARTICLE doi:10.3767/000651910X499240

Abstract In the course of revisionary work of Dendrobium section Formosae, we found some misinterpretations of Dendrobium kontumense. Dendrobium schildhaueri is placed as a synonym of D. kontumense and D. roseiodorum, a new species from Vietnam, is described.

Published on 16 April 2010

Key words: Dendrobium roseiodorum, new species, Orchidaceae, Vietnam

INTRODUCTION

Dendrobium Sw. sect. Formosae (Benth. & Hook. f.) Hook. f. (Orchidaceae), widely known by its synonymous name, sect. Nigrohirsutae (Lindl.) Schltr., comprises about 55 species and occurs from the Himalaya east to the Philippines and Sulawesi (Sathapattayanon, Yukawa & Seelanan, unpubl.). It is believed that sect. Formosae can be distinguished from the other Dendrobium sections by the presence of blackish hairs on leaf blades and leaf sheaths. However, several species from the Philippines and Borneo do not present this character. In fact, only the hard-textured flowers with white, greenish or yellow perianth lobes characterize the section (Yukawa 2004). A phylogenetic analysis of Dendrobium based on macromolecular data indicated the polyphyly of sect. Formosae (Wongsawad et al. 2005). These data suggest the necessity of re-examination of this section.

In the course of revisionary work of sect. Formosae, we have found misinterpretations of several species. Dendrobium kontumense Gagnep. is one of such obscure entities and has been variously interpreted in previous taxonomic treatments. For example, Kerr (1969) and Seidenfaden (1973, 1975) overlooked this species in their inventory works of Indochinese orchids. Subsequently, Seidenfaden (1985, 1992) placed D. kontumense as a synonym of D. virgineum Rchb.f. On the other hand, Schildhauer (2002) and Ormerod & Pedersen (2003) rejected this view and applied the name D. kontumense to another plant. In this study, we review these treatments and clarify the status of D. kontumense.

SYSTEMATICS

In 1930, Poilane collected Dendrobium material from Kon Tum Province, Vietnam. Gagnepain (1932) recognized its new status and described it as D. kontumense. Kerr (1969) and Seidenfaden (1973, 1975), however, overlooked this species and identified Laotian materials assignable to this species as D. sculptum Rchb. f., a Bornean species, because both species are similar in having white flowers with an orange blotch on the lip and a narrowly conical mentum. Later, Seidenfaden (1985) recognized his misidentification and reduced it to a synonym of D. virgineum, a species described from Myanmar (Reichenbach 1884).

On the other hand, Schildhauer (2002) demonstrated differences between D. kontumense and D. virgineum from sketches of the type material and from the original descriptions. He thus concluded that D. kontumense was not a synonym of D. virgineum but he misapplied the name D. kontumense to another entity, which is described here as a new species. Moreover, he did not recognize the differences between D. virgineum and the Indochinese material of D. virgineum sensu Seidenfaden.

Subsequently, Ormerod & Pedersen (2003) recognized the misinterpretation of D. virgineum by Schildhauer (2002) and described the Indochinese material of D. virgineum sensu Seidenfaden as a new species, D. schildhaueri Ormerod & H.A.Pedersen. As indicated by the history of interpretations of D. kontumense and D. virgineum, it is apparent that re-examinations of these species are needed.

First, we rechecked the holotype of D. virgineum (W) and found that it definitely belongs to D. infundibulum Lindl. complex (Sathapattayanon, Yukawa & Seelanan, unpubl.) and is not closely related to D. kontumense. We also found that the protologue and holotype of D. kontumense (Fig. 2e, f) completely agree with those of D. schildhaueri (Ormerod & Pedersen 2003). Vegetative parts of them are identical and they share floral features such as lanceolate-oblong sepals, elliptic petals, a narrowly conical mentum, a red central blotch on the glabrous lip and a transversely elliptic mid-lobe of the lip (Fig. 2c, d). From these evidences, we conclude that D. kontumense and D. schildhaueri represent the same taxon and that D. schildhaueri should be reduced to a synonym of D. kontumense.

Furthermore, we examined the plant identified as D. kontumense by Schildhauer (2002), Vestweber (2004) and Yukawa (2004) and compared it with the holotype of D. kontumense. We found that the flower of the former had densely verrucose calli on the lip, the golden yellow to orange side lobes and central part of a mid-lobe of the lip, a widely obovate mid-lobe narrower than side lobes of the lip, whereas the flower of the holotype of D. kontumense showed a glabrous lip, having only 3-5 slightly raised veins on the disc, a shape of mid-lobe more or less the same size as the side lobes of the lip. Moreover, an apical part of the lip of the former is more recurved and thicker than that of D. kontumense. We therefore recognized this plant as a new species, D. roseiodorum A.Sathapattayanon, T.Yukawa & T.Seelanan.

Fig. 1 Dendrobium roseiodorum A.Sathapattayanon, T.Yukawa & T.Seelanan. a. Habit; b. hairs on leaf; c. flower bud, side view; d. flower, front view; e. flower, side view; f. flower, from below; g. lip and mentum, side view, sepals and petals removed; h. lip and mentum, from above, sepals and petals removed; i. dorsal sepal; j. petal; k. lateral sepal; l. lip; m. lip, note the verrucose calli on the disc; n. floral bract; o. column and column foot, side view; p. column and column foot, from below; q. column, from below, operculum removed; r. operculum; s. pollinia (all from Hort. Tsukuba Botanical Garden accession number 188269 (holotype)). - Drawing by Mr. Tanucha Boonjaras.

Dendrobium kontumense and the new species constitute a monophyletic group with D. draconis Rchb.f., D. ochraceum De Wild. and D. trankimianum T.Yukawa as demonstrated by a molecular phylogenetic analysis of Dendrobium sect. Formosae (Sathapattayanon, Yukawa & Seelanan, unpubl.). They share the following floral characters: a slender, narrowly conical mentum, a dilated base of the column and a raised margin of the column foot. The results of phylogenetic analyses further show that D. roseiodorum is most closely related to D. ochraceum. In fact, a synapomorphic morphological character, verrucose calli on the lip, also indicates their sister group relationship. However, several floral features of D. roseiodorum distinctly differ from D. ochraceum. The new species has a substantially golden yellow to orange lip (Fig. 2a), whereas D. ochraceum has a creamy yellow flower with scarlet veins on the lip (Fig. 2g). Further, they are distinguishable by the shape of the petals (elliptic-rhombic in D. roseiodorum; narrowly elliptic in D. ochraceum), the shape of side lobes of the lip (obliquely ovate in D. roseiodorum; obliquely elliptic in D. ochraceum, shown in Fig. 2h) and the verrucose calli of the lip (on the disc and veins in D. roseiodorum, shown in Fig. 2b; only on the veins in D. ochraceum, shown in Fig. 2h).

1. Dendrobium roseiodorum A.Sathapattayanon, T.Yukawa & T.Seelanan, sp. nov.- Fig. 1, 2a, b

Dendrobium ochraceum de Wild. affine, sed petalis ellipticis-rhombicis, labello aureo-aurantiaco, et disco labelli verrucoso diversum. - Typus: Hort. Tsukuba Botanical Garden accession number 118269 (holo TNS; iso BCU), Vietnam, sine loc., 15 September 2008.

Dendrobium kontumense auct. non. Gagnep.; Schildhauer (2002) 369; Vestweber (2004) 38; Yukawa (2004) 23, f. 3-4.

Plant erect, 30-40 cm high. Roots elongate, 1.8-2.1 mm diam, branched, white to grey. Pseudobulbs clustered, narrowly fusiform, 30-37 cm long, 1.1-1.4 cm diam, slightly flexuose, weakly sulcate in age, leafy throughout, almost entirely covered by persistent leaf sheaths, with 7-18 internodes. Leaves distichous; blade patent, slightly recurved, coriaceous, lanceolate, 4.7-9.1 cm long, 0.9-1.9 cm wide, apex unequally bilobed, entire, dark green, both surfaces covered with dense hirsute hairs rubbing off with age, adaxial hairs brownish, abaxial hairs blackish; sheaths 3-3.4 cm long, brownish green, abaxial hairs blackish and rubbing off with age. Inflorescences abbreviated raceme, terminal or axillary on apical part of pseudobulbs, (1-)2-5-flowered; peduncle inconspicuous, 3-4 mm long, entirely enclosed by bracts; rachis 5-7 mm long; floral bracts ovate-triangular or lanceolate-triangular, 10.3-10.5 mm long, 4-7 mm wide, acuminate, concave, brownish, abaxial surface with brown hairs, adaxial surface glabrous. Flowers glossy, sweetly scented, 4.3-4.8 cm diam; sepals and petals white; lip golden yellow, apical part white, veins on side lobes and disc orange; column and operculum golden yellow to orange; column foot reddish orange; pollinia bright yellow; pedicellate ovary white. Median sepal spreading recurved at apical part, ovate-lanceolate, 2.4-3 cm long, 0.9-1.3 cm wide, abruptly acute, abaxial surface 1-keeled, 5-7-nerved. Lateral sepals twisted and recurved, obliquely lanceolate-triangular, abruptly acute to mucronate, abaxial surface 1-keeled, 5-7-nerved, anterior margin 2.6-3.5 cm long, posterior margin 5.5-6.7 cm long, 1-1.3 cm wide at base; mentum narrowly conical, ovipositor-shaped, 2.5-2.8 cm long, straight to upcurved. Petals slightly twisted and recurved at apex, elliptical-rhombic, 2.6-3.2 cm long, 1.4-1.6 cm wide, obtuse, undulate, 5-9- nerved. Lip 3-lobed, 4.7-5.1 cm long, 1.7-1.8 cm wide across side lobes; claw narrowly triangular, 1.5-2 cm long; side lobes upcurved, obliquely ovate, puberulent at base, rounded, entire, adaxial surface with 4-5 veins running along each side and sparsely verrucose; mid-lobe thick, widely obovate, 1-1.2 cm long, 1.1-1.5 cm wide, obtuse when flattened, conduplicated and recurved at apical part, undulate, adaxial surface densely verrucose at median ridge. Column glabrous, dilate at base, 7-8 mm long, 5.5-6 mm wide at base; stelidia short, triangularfalcate, obtuse; connective narrowly triangular, column foot 4.5-5.1 mm long, grooved, papillose; operculum cucullate, very widely obovate, 3-3.2 mm long, 3-3.1 mm wide, obtuse, base ciliate, dorsally sulcate, densely papillose; pollinia 4, in 2 pairs, 1.8-2 mm long. Pedicellate ovary clavate, 3.2-4.1 cm long, curved, slightly sulcate, glabrous. Fruit not seen.

Distribution - Vietnam (Khanh Hoa Province and Lâm Dong Province).

Habitat & Ecology - Recorded on boulders or tree branches; 1000-1200 m altitude. Flowering: September to November (in natural habitat), July to December (in cultivation).

Etymology - The specific epithet refers to the rose-like floral scent of the new species.

Other specimens studied. Vietnam. Poilane 46633 (P) Khanh Hoa Province, Nha Trang, 1075 m alt., 17 Sept. 1922; S. Khruekerd KV-0012 (TNS), Lâm Dong Province, Lang Bian Mountain; Oct.a.2005/12385 (Photograph seen) Lâm Dong Province, Oct. 2005; Hort. Tsukuba Botanical Garden accession number 144309 (TNS), sine loc., 26 July 2007; Hort. Tsukuba Botanical Garden accession number 144422 (TNS), sine loc.

2. Dendrobium kontumense Gagnep. - Fig. 2c-f

Dendrobium kontumense Gagnep. (1932) 165; (1934) 239; Seidenf. (1975) 46. - Type: Poilane 18280 (holo P; iso C), Vietnam, Kon Tum Province, Giang Lo to Dac To, 500 m alt., 8 September 1930.

Dendrobium schildhaueri Ormerod & H.A.Pedersen (2003) 341; Vestweber (2004) 35; H.P.Wood (2006) 691, pl. 140, syn. nov. - Type: sine coll. GT 9301 (holo C), Thailand, Nong Khai Province, Seka, October 1983.

Dendrobium sculptum auct. non. Rchb. f.; A.D. Kerr (1969) 193; Seidenf. (1973) 123; (1975) 51.

Dendrobium virgineum auct. non. Rchb.f.; Seidenf. (1985) 112, f. 68; (1992) 211, f. 134; Aver. (1990) 83; (1994) 182; Rakpaibulsombat (1992) pl. 30; M.L.Baker & C.O.Baker (1996) 758; Thaithong (1999) 127; (2000) 231; Dân Tôc (2000) 102; Lavarack (2001) 13; Alsagoff & Hong (2001) 73, including photo 5 on p. 70; Schildh. (2002) photo on p. 371; Aver. & Averyanova (2003) 31; (2005) 60; Vaddhanaphuti (2005) 131.

Distribution - Thailand (Nakorn Phanom Province, Nong Khai Province, Ubon Ratchathani Province), Laos (Vientiane Province), Vietnam (Lâm Dong Province).

Habitat & Ecology - Epiphyte in dry evergreen forests; 500-1000 m altitude. Flowering: July to October.

Note - The flower is white with a small central blotch on the lip, which varies in colour from very pale to reddish orange.

Other specimens studied. Thailand: Sakdi 4500 (C), Nong Khai Province, Phu Wua, Aug.-Sept. 1983; sine coll. GT 9307 (C), Ubon Ratchathani Province, 13 Sept. 1983; Sakdi GT 8952 (C), Nong Khai Province, Phu Wua, 17 July 1984; sine coll. GT 9301 (C), Nong Khai Province, Seka, 14 Aug. 1984; Saki GT 8967 (C), sine loc., 16 July 1985; O. Thaithong 737 (BCU) sine loc., 26 Aug. 1989; A. Sathapattayanon 408 (BCU) Nong Khai Province, Phu Wua, 1 Aug. 2005; A. Sathapattayanon 435 (BCU) Nong Khai Province, Phu Wua, 17 Aug. 2006; O. Thaithong s.n. (BCU), sine loc.; Sukhakul GT 8993 (C), Nakorn Phanom Province. - Laos: Delacoeur 177 (P), sine loc., 1928; A.D. Kerr s.n. (K), Vientiane Province, Phou Khaokhoay, 16 Aug. 1966; A.D. Kerr 984 (K), sine loc., 10 Oct. 1966; Vidal 5585 (P), Vientiane Province, Phou Khaokhoay, 900 m alt., 29 Oct. 1971; A.D. Kerr 988 (C), Vientiane Province, Phou Khaokhoay. - Vietnam: Darlac cult. Vadherst s.n. (P), sine loc., Apr. 1940; Oct.a. 2005/12418 (photograph seen), Lâm Dong Province, Oct. 2005; HAL 8632/13249 (photograph seen), Lâm Dong Province. - Locality unknown: Hort. Tsukuba Botanical Garden accession number 126642 (TNS); Hort. Tsukuba Botanical Garden accession number 119105 (TNS); Hort. Tsukuba Botanical Garden accession number 118828 (TNS).

Fig. 2 a, b. Dendrobium roseiodorum A. Sathapattayanon, T. Yukawa & T. Seelanan (holotype). a. flowers; b. lip, note the verrucose calli on the disc. - c, d. Dendrobium kontumense Gagnep. c. flower; d. lip. - e, f. Dendrobium kontumense Gagnep. (holotype). e. flower, boiled; f. lip, boiled. - g, h. Dendrobium ochraceum de Wild. g. flower; h. lip, note the obliquely elliptic side lobes of the lip and the verrucose calli on the veins (a, b: Hort. Tsukuba Botanical Garden accession number 144309; c, d: A. Sathapattayanon 408; e, f: Poilane 18280; g, h: Hort. Tsukuba Botanical Garden accession number 122822).

Additional specimen studied. Dendrobium draconis Rchb. f.; Myanmar: Parish 1365 (holo W), Mawlamyine (formerly called Moulmein); Thailand: A. Sathapattayanon 371 (BCU), Ubon Ratchathani Province, Pha Taem National Park, 800 m alt., 29. Nov. 2004, A. Sathapattayanon 388 (BCU), Tak Province, Umphang Wildlife Sanctuary, 970 m alt., 28 Feb. 2005. - Dendrobium ochraceum De Wild.; Vietnam: G. Bronckart s.n. (holo BR; iso C), Tonkin, 500 m alt., 1905; Hort. Tsukuba Botanical Garden accession number 122822 (TNS), sine loc., 11 May 2007. - Dendrobium trankimianum T.Yukawa: Vietnam: Hort. Tsukuba Botanical Garden accession number 127511 (holo TNS), Borders of Lâm Dong, Khanh Hoa and Ninh Hoa Province, 800-1000 m alt., Apr. 2000. - Dendrobium virgineum Rchb. f.; Myanmar: Low cult. s.n. (holo W), sine loc., Oct. 1884.

Acknowledgements

This work was kindly supported by the 90th Anniversary of Chulalongkorn University Fund, Ratchadaphiseksomphot Endowment Fund, Graduate School, Chulalongkorn University (3000047) and also supported by the Thai government budget 2006, under the Research Program on Conservation and Utilization of Biodiversity and the Center of Excellence in Biodiversity, Faculty of Science, Chulalongkorn University (CEB_D_10_2006). This study was also partly supported by a Grant-in-Aid to Scientific Research from the Japan Society for the Promotion of Science to T. Yukawa. We are indebted to the directors and curators of AUU, BCU, BM, BR, C, E, K, L, P, SING, TNS and W for making their collections available for study. Dr. Obchant Thaithong, Prof. Dr. Leonid V. Averyanov, Dr. Hul Sovanmoly, Dr. Henrik A. Pedersen and Mr. André Schuiteman are gratefully acknowledged for their kind assistance and valuable suggestions during our study. We wish to express our grateful thanks to Mr. Kazuhiro Suzuki for his skilful cultivation of this orchid group. Our thanks are also extended to Tran Kim Khanh and Subhkon Khruekerd for providing the material, Mr. Tanucha Boonjaras for the line drawing and Ms. Suchada Wongpakam for improving the manuscript.

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^[1] Biological Science Program, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand; corresponding author e-mail: dao23rd@yahoo.com.

^[2] Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.

^[3] Tsukuba Botanical Garden, National Museum of Nature and Science, 1-1, Amakubo 4, Tsukuba 305-0005, Japan.