KEW BULLETIN VOL. 64: 747–750 (2009) Arundinella kokutensis (Poaceae, Arundinelleae), a new species from south-eastern Thailand Atchara Teerawatananon1,3, Sarawood Sungkaew2 & Trevor R. Hodkinson3 Summary. Arundinella kokutensis Teerawat. & Sungkaew is described and illustrated here as a new species from Kut Island, Trat Province, Thailand. Key Words. Arundinella, Gramineae, Poaceae, Thailand. Introduction The genus Arundinella was established by Raddi (1823) based on the type species Arundinella brasiliensis Raddi collected from Brazil but now recognised as A. hispida (Willd.) Kuntze. This genus is distinguished by its paired, 2-flowered spikelets which disarticulate above the glumes, scabrid upper lemmas, punctiform hilums and short membranous ligules. Clayton & Renvoize (1986) reported that there are about 50 species of Arundinella, distributed chiefly in Asia, an estimate that has now been raised to approximately 60 species (Sun & Phillips 2006). Among the specimens of the genus Arundinella collected from Thailand, a very distinctive collection, Charoenphol et al. 5104 from Kut Island, Trat Province, Southeastern Thailand was previously labelled as Arundinella metzii Hochst. ex Miq. After re-collecting and critically examining both living and herbarium specimens, from the same locality, their morphology could not be matched with the species descriptions or type specimens of A. metzii (Hohenacker 297 (K)), nor any other Arundinella species. Neither do they fit within the natural range of morphological variation found within those other species. Therefore, a new species A. kokutensis Teerawat. & Sungkaew is described here. Arundinella kokutensis Teerawat. & Sungkaew sp. nov. Species A. metziae Hochst. ex Miq. et A. holcoidi (Kunth) Trin. affinis, sed ab illis ramis et pedicellis fere glabris, glumis imus glabris, aristis lemmatium superiorium 5 – 6.5 mm longis, staminibus 2 differt. Typus: Charoenphol et al. 5104 (holotypus K!; isotypi BKF!, C!, E!, NY!). Annual. Culms slender, 5 – 80 cm tall, erect, shortly decumbent at base; nodes sparsely pubescent. Leafsheaths 2 – 8 cm long, hispid with tubercle-based hairs especially along margins. Ligule a ciliate membrane, 0.8 – 1.3 mm long. Leaf-blades oblong-lanceolate, (1 −) 5 – 30 × (0.3 −) 0.6 – 1.3 cm, hispid with tuberclebased hairs on both surfaces, margins sometimes scaberulous. Panicles open, sometimes drooping, (3 −) 10 – 25 cm long; racemes (2 –) 4 − 10 cm long, alternate, rhachis almost glabrous, rarely scabrous. Spikelets green, ovate-lanceolate, 3 – 4 × 0.6 – 1 mm; pedicels 0.5 – 6 mm long, glabrous; lower glumes ovatelanceolate, 2 – 2.5 × 0.5 – 1 mm, almost glabrous, sometimes scabrous at apex, acuminate to aristate, 3 – 5-nerved; upper glumes ovate-lanceolate, 3 – 3.5 (− 4) × 0.5 – 1 mm, glabrous to sparsely hispid with tuberclebased hairs, caudate, recurved, 5-nerved; lower florets barren; lower lemmas ovate-lanceolate, 2 – 2.5 mm long, acute, 5-nerved; lower paleas ovate-oblong to ovatelanceolate, 1.5 – 2 mm long; upper lemmas ovateoblong, 1 – 1.5 mm long, minutely bifid, awned from the sinus, awns 5 – 6.5 mm long, 3-nerved; upper paleas ovate-lanceolate, 1.2 – 1.4 mm long, acute; callus hairy, hairs 0.3 – 0.5 mm long; stamens 2 rarely 3, anthers yellow, 0.3 – 0.5 mm long; styles 2, stigmas purple, 0.5 – 0.7 mm long. Caryopsis ovoid-elliptic, 1 – 1.2 mm long. Fig. 1. DISTRIBUTION. Endemic to Thailand. SPECIMENS EXAMINED. THAILAND. Trat: Ko Kut, (12° 35'N 101°31'E), 21 Nov. 1970, Charoenphol et al. 5104 (BKF, C, E, K, NY); loc. cit., 3 April 2006, Teerawatananon & Sungkaew 914 (BKF, TCD, Herbarium of Accepted for publication September 2009. 1 Natural History Museum Thailand, National Science Museum, Technopolis, Pathum Thani, 12120, Thailand. e-mail: teerawaa@tcd.ie 2 Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkhen, Bangkok, 10900, Thailand. e-mail: sarawoodsungkaew@yahoo.com 3 Department of Botany, School of Natural Sciences, Trinity College, University of Dublin, Dublin 2, Ireland. e-mail: hodkinst@tcd.ie © The Board of Trustees of the Royal Botanic Gardens, Kew, 2010 748 KEW BULLETIN VOL. 64(4) Fig. 1. Arundinella kokutensis. A habit; B inflorescence; C spikelets; D lower glumes; E upper glumes; F lower lemmas; G lower paleas; H upper lemmas; J upper paleas. All from Charoenphol et al. 5104. DRAWN BY ATCHARA TEERAWATANANON. © The Board of Trustees of the Royal Botanic Gardens, Kew, 2010 glabrous or pubescent up to 50 cm, an open panicle scabrous scabrous c. 1 mm long 0.4 – 0.5 mm long c. 3 mm long 3 hirsute 3 – 15 (− 20) cm long, a narrow panicle scabrous and pilose with tubercle-based hairs glabrous, sometimes sparsely pilose 1 – 1.3 mm long 0.2 – 0.3 mm long 4 – 4.5 mm long 3 sparsely pubescent (3 −) 10 – 25 cm long, an open panicle, sometimes drooping almost glabrous, rarely scabrous glabrous 1 – 1.5 mm long 0.3 – 0.5 mm long 5 – 6.5 mm long 2 (extremely rarely 3) Nodes Inflorescence Rhachis Pedicels Upper lemmas Callus hairs Awns Stamens A. holcoides A. kokutensis Species/ Characters Table 1. Morphological variation in Arundinella kokutensis and its close relatives, A. holcoides and A. metzii. A. metzii ARUNDINELLA KOKUTENSIS (POACEAE, ARUNDINELLEAE), A NEW SPECIES FROM SOUTH-EASTERN THAILAND 749 Thailand Natural History Museum, National Science Museum & 3 April 2006, Teerawatananon & Sungkaew 917 (TCD, Herbarium of Thailand Natural History Museum, National Science Museum). HABITAT. Growing on shaded, moist and mossy granite rocks, along streams in tropical monsoon rainforest. ETYMOLOGY. This species is named after the island (‘Ko’ in Thai) called Kut, Trat Province, southeastern Thailand, where this plant was collected for the first time. CONSERVATION STATUS. Arundinella kokutensis is extremely restricted in distribution and specific habitat, occurring in small populations. It is very likely an endemic to Ko Kut. We recommend treating this species as Vulnerable (VU) D1 D2 until more data are obtained. NOTES. Arundinella kokutensis has only two stamens instead of three as normally found in other species of the genus (Keng 1936; Bor 1955; Watson & Dallwitz 1992; Clayton et al. 2006; Sun & Phillips 2006). Occasional florets with three stamens can be found but the occurrence is extremely rare within an inflorescence that predominantly contains florets with two stamens. This species is similar to A. holcoides and A. metzii but can be distinguished from them by its almost glabrous rhachis, a glabrous pedicel, an awn of the upper lemma which is longer (5 – 6.5 mm long), and its stamen number which is only two. The differences between A. kokutensis, A. holcoides and A. metzii are summarised in Table 1. Acknowledgements The authors are grateful to the curators and the staff of the following herbaria: BKF, C, E, K, and NY for the use or loan of specimens. Thanks to Prof. Dr Pranom Chantaranothai for his kind comments and useful suggestions, to Prof. John Parnell and Dr Pimwadee Pornpongrungrueng for their support of the work, and Prof. Dr Benjamin Øllgaard for help with the Latin diagnosis. This work was supported by the TRF/ BIOTEC Special Program for Biodiversity Research and Training Grant T_148026. References Bor, N. L. (1955). Notes on Asiatic grasses XXIV: the genus Arundinella Raddi in India, Burma and Ceylon. Kew Bull. 2: 377 – 414. Clayton, W. D. & Renvoize, S. A. (1986). Genera Graminum, Grasses of the World. Kew Bull. Addit. Ser. 13: 1 – 389. ____, Harman, K. T. & Williamson, H. (2006 onwards). GrassBase- The Online World Grass Flora. Version: 25 Aug. 2008. http://www.kew.org/data/grasses-db. html. © The Board of Trustees of the Royal Botanic Gardens, Kew, 2010 750 Keng, Y. L. (1936). Asiatic species of Arundinella. National Central University. Science Reports 2: 1 – 68. Raddi, G. (1823). Agrostographia brasiliensis. Bertini, Lucca. Sun, B. & Phillips, S. M. (2006). Arundinella. In: Z.-Y. Wu, P. H. Raven & D.-Y. Hong (eds), Flora of China, Vol. 22 (Poaceae). Science Press, Beijing, Peoples © The Board of Trustees of the Royal Botanic Gardens, Kew, 2010 KEW BULLETIN VOL. 64(4) Republic of China and Missouri Botanical Garden Press, St Louis, Missouri, USA. Watson, L. & Dallwitz, M. J. (1992 onwards). Grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 7 April 2008. http://delta-intkey.com.