THAI FOR. BULL. (BOT.) 42: 100–103. 2014. Porpax thaithongiae (Orchidaceae) a new species from Thailand SOMRAN SUDDEE1, PHATTARAVEE PROMMANUT2 & SANTI WATTHANA3 ABSTRACT. Porpax thaithongiae, a new species from the degraded limestone hills in Umphang District, Tak Province in the western part of Thailand is described and illustrated. KEY WORDS: Porpax, new species, Orchidaceae, Thailand. INTRODUCTION Sterile plants of this new attractive epiphytic orchid were discovered during a plant collecting trip to Doi Hua Mot, Umphang District, Tak Province, in the western part of Thailand more than 10 years ago, but the irst lowering material was only found during a plant collecting trip in April 2013. The plants were found mostly on tree trunks in degraded limestone hills in dry deciduous dipterocarp forest where forest ire occurs nearly every year. The area also has a high rate of erosion because of trekkers and over grazing by cattle. This new taxon belongs to the genus Porpax Lindl. but does not match any of the known species in Porpax, and so is described and illustrated here. Porpax Lindl. is a genus of epiphytes, distributed mainly in tropical regions of Asia, from the Himalayas to India, Nepal, Bhutan, S China, Laos, Thailand, peninsular Malaysia and Sabah (Pridgeon et al., 2005). An overall treatment was done by Seidenfaden (1986), in which 11 species were recognized with 7 species from Thailand; P. elwesii, P. gigantea, P. grandilora, P. lanii, P. parishii, P. scaposa and P. ustulata. Seidenfaden (1992) reported 3 species in Indochina; P. elwesii, P. ibuliformis and P. reticulata. Seidenfaden & Wood (1992) reported one species, P. elwesii for Peninsular Malaysia and Singapore. Sitthisajjadham and Tripetch (2009) reported another species, P. meirax, from the western part of Thailand. DESCRIPTION Porpax thaithongiae Suddee, Prommanut & Watthana sp. nov. Closely related to Porpax lanii in having all sepals connate nearly to the apex, but differs in having the sepal tube wide open and glabrous; labellum ovate, distinctly 3-nerved; petals ovate, 3-nerved, inely rugose at apex, broadly clawed at base. Also closely related to Porpax elwesii in having having all sepals glabrous and connate nearly to the apex, but differs in having inlorescence appearing from the base of pseudobulb instead of from the apex. Type: Thailand. Tak Province, Umphang District, Doi Hua Mot: 879 m alt., 13 April 2013, Suddee, Rueangruea, Prommanut & Pansamrong 4433 (holotype BKF). Fig. 1 & 2. Plant epiphytic, clump-forming on the substrate, 2.5–5 cm tall. Pseudobulbs lattened triangular to globose, 0.8–1.6 cm in diam., covered by a sheath which disintegrate into a ibrous reticulate network. Foliage leaves 2 per pseudobulb, often appearing after the lower, elliptic to oblong, 0.8–3.5 by 0.6–1.2 cm, apex acute, base tapering to a 1 The Forest Herbarium (BKF), Department of National Parks, Wildlife and Plant Conservation, Chatuchak, Bangkok 10900, Thailand. 2 Bangkok Herbarium (BK), Department of Agriculture, Bangkok 10900, Thailand 3 Queen Sirikit Botanic Garden (QBG), The Botanical Garden Organization, Chiang Mai 50180, Thailand PORPAx THAITHONGIAE (ORCHIDACEAE) A NEW SPECIES FROM THAILAND (S. SUDDEE, P. PROMMANUT & S. WATTHANA) 101 Figure 1. Porpax thaithongiae Suddee, Prommanut & Watthana, A. Plants in lower with a fruit from the previous year; B. Plants in fruit; C. Flower side view; D. Flower front view; E. Bract abaxial surface; F. Dissected lower longitudinal section; G. Sepals abaxial surface; H. Petal abaxial surface; I. Petal adaxial surface; J. Labellum; K. Column; L. Operculum from above; M. Operculum from below; N. Pollinia. A, C–N from Suddee et al. 4433 (BKF); B from Prommanut 307 (BKF). All drawn by P. Prommanut. 102 THAI FOREST BULLETIN (BOTANY) 42 A B C D E F Figure 2. Porpax thaithongiae Suddee, Prommanut & Watthana, A–E. Plants in lower; F. Plants in fruit. A by S. Rueangruea; B–F by P. Prommanut. PORPAx THAITHONGIAE (ORCHIDACEAE) A NEW SPECIES FROM THAILAND (S. SUDDEE, P. PROMMANUT & S. WATTHANA) petiole, lamina dull green, with faint longitudinal lines; petiole 2–3 mm long. Inlorescence short, arising from base of pseudobulb, 1-lowered; peduncle very short; loral bracts conspicuous, ovate to rounded, 3–6.5 by 2–5 mm, apex acute, covering ovary. Flower 0.8–1 cm long, dull red, occasionally yellow; pedicel and ovary short. Sepals connate into a subcampanulate tube, wide open, usually with several shallow keels outside, glabrous, gibbous at base; lobes broadly ovate, apiculate at apex. Petals ovate, 2.5–3 by 1.8–2.5 mm, 3-nerved, apex acute and inely rugose, broadly clawed at base. Labellum simple, ovate, 2.8–3.5 by 2–2.5 mm, recurved, distinctly 3-nerved, warty and shortly laciniate along margins; disk ornamented by irregular calli. Column 1.5–2 mm long, foot long; rostellum large, truncate; operculum tuberculate; pollinia 8, in 2 groups of 4, laterally compressed. Capsule subglobose, 6–7 mm in diam., with 3 longitudinal ridges. Thailand.— NORTHERN: Tak [Umphang District, Umphang Wildlife Sanctuary, Doi Hua Mot, 879 m alt., 13 April 2013, Suddee, Rueangruea, Prommanut & Pansamrong 4433 (BKF); ibid, 3 July 2013, Prommanut 307 (BKF)]. Distribution.— Endemic (known only from the type locality). Phenology.— Flowering: April–May. Ecology.— Dry deciduous dipterocarp forest on degraded limestone hills; 800–900 m alt. Vernacular.— Ueang rangnok thai thong (เอื้องรังนกไทยทอง). 103 Etymology.— Porpax thaithongiae is named in honour of Assoc. Prof. Dr Obchant Thaithong of the Department of Botany, Chulalongkorn University, who has long contributed to Thai orchids study. Conservation.— DD (Data Deicient). More exploration is needed in order to gain more information for conservation assessment. ACKNOWLEDGEMENTS We would like to thank Sukid Rueangruea and Pongsiri Pansamrong for their assistances in the ield and for making the trips enjoyable. Bob Harwood and Andre Schuiteman are also thanked for useful comments. REFERENCES Pridgeon, A.M., Cribb, P.J., Chase, M.W. & Rasmussen, F.N. (eds). (2005). Genera Orchidacearum 4. Oxford University Press, Oxford. Seidenfaden, G. 1986. Orchid Genera in Thailand xIII. Thirty-three epidendroid Genera. Opera Botanica 89: 118–123. Seidenfaden, G. 1991. The Orchids of Indochina. Opera Botanica 114: 192–193. Seidenfaden, G. & Wood, J. J. 1992. The Orchids of Peninsular Malaysia and Singapore. Olsen & Olsen, Fredensborg. Sitthisajjadham, S. & Tripetch, P. 2009. Wild Orchid of Thailand 2 (in Thai). Amarin Printing and Publishing, Bangkok.