SANDAKANIA 1 (1992) : 1-6 Racemobambos pairinii (Gramineae : Bambusoideae). a new species of bamboo from Sabah, Malaysia KM_ Wong Forest Research Centre, Sepilok, P.O. Box 1407, 90008 Sandakan, Sabah, Malaysia Summary. Racemobambos pairinii is described as a new species, so far collected only from a few localities on ultramafic soil in the central and eastern parts of Sabah, Malaysia, in north Borneo. Notes on differences from other species of the genus, and on its flowering, distribution and conservation, are provided. The genus Racemobambos was established by Holttum (1956), and was typified by R. gibbsiae (Stapf) Holtt. which occurs on Mt Kinabalu. Sabah. Thus far, sixteen species have been recognized in the genus (Holttum 1956; Dransfield 1980, 1983, pers. comm. 1992). Nearly all the species have an elegant habit, with culms that are pencil-thin or only slightly thicker. The majority are highly localized and, thus, rare species, and mostly occur at upper altitudes on mountains. Of the sixteen species that have been described, six occur in Borneo: R. gibbsiae, R. glabra Holtt., R. hepburnii Dransf., R. hirsuta Holtt., R. kutaiensis Dransf. and R. rigidifolia Holtt. Except for R. kutaiensis, recorded with only one collection from Kalimantan, these are also found in Sabah (Dransfield 1983; Kulip 1992). In her revision of the genus. Dransfield (1983) included three specimens (SD 779, SD 780, SD 786) under R. hirsuta. With more material from a recent collection of the taxon conspecific with these specimens, as well as of typical R. hirsuta, it is now possible to differentiate the two taxa as distinct species. The new species and R. hirsuta were both discovered on Mt. Nicola in the Danum Valley Conservation Area in the eastern part of Sabah, during an expedition there in February, 1992. Their occurrence at the same locality permitted easy comparison of the living plants and fresh flowering material. Distinguishing characters for the new species The elegant new species, named Racemobambos pairinii below in honour of Sabah's Chief Minister, Datuk Sri Joseph Pairin Kitingan, belongs to a group of species characterized by spikelets with two glumes each: R. hirsuta and R. rigidifolia from Borneo, and R. setifera Holtt. from Peninsular Malaysia. R. rigid/folia and R. setifera have glabrous spikelets and are thus different from R. hirsuta and R. pairinii, which have hairy spikelets. The latter two can be rapidly distinguished in the field because R. hirsuta has bristly auricles on the culm and leaf sheaths, whereas R. pairinii has glabrous auricles on the sheaths. Table 1 lists the differences between R. hirsuta and R. pairinii. TABLE 1. Morphological differences between Racemobambos hirsuta and R. pairinii. R. hirsuta R. pairinii Culm-sheath auricles small, CUlm-sheath auricles nil, lobe-like and bristly glabrous Leaf-sheath auricles small, Leaf-sheath auricles nil, bristly glabrous Leaf-sheath ligules Leaf-sheath ligules elongate, inconspicuous obtuse Spikelets held closely to SplKelets conspicuously curved the main inflorescence away from the main axis inflorescence axis Lemmae shorter (5-8 mm Lemmae longer (10-16 mm long), long), hardly overlapping overlapping along the along the spikelet spikelet Paleae longer than lemmae Paleae as long as or shorter than lemmae Palea 4-veined on the back Palea 2-veined on the back between keels, and between keels, and 3-veined 4-veined on each wing on each wing Cilia on the palea keels Cilia on the palea keels 0.2-0.3 mm long hardly 0.1 mm long Mature anthers only 4-5 mm Mature anthers 6-8 mm long long 2 The new species described Racemobambos pairinii, sp. nov. R. hirsuta Holtt. affinis, sed lemmatibus longioribus (10 16 mm) palea aequantibus vel superantibus, antheris longioribus (6-8 mm), auriculis vaginae culmorum et foliorum nu/lis, ligulis foliorum longioribus obtusus differt. Typus: Wong et al. WKM 2106 (holorypus SAN). Slender bamboo in clumps of open habit. with culms clambering or flopping over surrounding plants. to 4 m high. Rhizomes sympodial. slender with elongated necks 1·5 cm long. Culms 5-9 mm diameter. to 4-5 m long. green; internodes 30-40 cm long. glabrous. slightly white-waxy below the nodes. Branch complement with a dominant middle branch which grows reiteratively like the culm itself. and 1-2 smaller secondary branches from its base on each side. Culm-sheaths 5-16 cm long. green. glabrous. slightly white-waxy; auricles not developed; ligule a subentire rim 0.5-1 mm high; blades green. linear. 2-10 cm long. 2-4 mm wide. spreading to reflexed. Leaf blades 6-22(-30) cm long. 0.8-2.0(-3.4) cm wide; auricles not developed; ligule elongate and obtuse. 1-2(-4) mm long. glabrous. Inflorescence semelauctant. 8-11 cm long when fully developed. the spikelets individually stalked and arranged alternately along the main axis terminating leafy branchlets; main axis Short-hairy all over. Spikelets 2.5-4.5 cm long when mature. conspicuously outcurved from the main inflorescence axis. with 2 glumes. 4-5 perfect flowers and a terminal vestigial flower (usually represented by a tightly rolled lemma). green to purplish green; rachilla internodes 3-6 mm long. shortest at the base of the spikelet. minutely hairy; lower glume narrow. small. 4-8 mm long. asymmetric. the broader wing thin and 1-veined. the narrower thick. short-hairy on the margin and median vein; upper glume 10-13 mm long. mucronate. chartaceous. Short-hairy on the margin and back near the apex; lemmae 7-16 mm long. mucronate. coriaceous. longest at the base of the spikelet. overlapping along the spikelet. 6-7-veined. short-hairy on the margin and back; paleae 7-8 mm long. membraneous. apex blunt, 2-keeled (keels closest at the base). 2-veined on the back. 3-veined on each wing. minutely ciliolate on the keels (cilia hardly 0.1 mm long), minutely hairy on the back; lodicules 3. basally thickened. apically membraneous. ciliate on the margin, the anterior c. 3 mm long and 1.5-2 mm wide. the posterior two 1.5-2 mm long and c. 1 mm wide; stamens 6. filaments free. anthers 6-8 mm long when mature and fully extruded, connective not prolonged beyond apex; ovary narrowly cylindrical to narrowly ovoid. 0.5 1.5 mm long, glabrous; stigmas 3. 3-6 mm long. The species is illustrated in Fig.1. SPECIMENS EXAMINED - BORNEO. SABAH: Telupid, road to Karamuak Valley. 50m, flowering. 24 Oct. 1979. S. Dransfield SD 779 (BO. K. KEP, SAN, SAR); vegetative, 24 Oct. 1979. SD 780 (K. SAN). Lahad Datu, Bukit Silam. 100 m, vegetative. 1 Nov. 1979. S. Dransfield SD 786 (K. SAN); Danum Valley Conservation Area. Mt Nicola. 530·800 m. flowering. 24 Feb. 1992. Wong. Kulip. Radin. Madani. Berhaman. Molubin and Tokilip WKM 2106 (holotype SAN; isotypes K. KEP. L. SAR. SING). 3 L N J~ A Fig. 1. Racemobambos pairinii. A, culm shoot; B, culm sheath; C, leafy and flowering branches; D, detail, leaf-sheath ligule; E, branch complement; F, spikelet; G, lower glume; H, upper glume; J, lemma; K, palea, back view; L, palea, front view; M, lodicule complement; N, stamens; P, gynoecium. All from WKM 2106. Aowering, distribution and prospects for conservation At the end of February, 1992, many clumps of R. pairinii on Mt Nicola were beginning to flower, apparently following in the wake of the gregarious flowering of the entire R. hirsuta population around the summit at 870-910 m. Previously, only the species R. gibbsiae and R. hepburnii on Mt Kinabalu have been definitely documented as flowering gregariously (Wong, Chan and Phillipps 1988), a habit that intersperses several to many years in between flowering episodes. A general flowering of any Racemobambos population would appear to be a rare event. On Mt Nicola seedlings were observed in fully flowering stands of R. hirsuta at the summit, but apparently had not yet become common in stands of R. pairinii that were just coming into flower R. pairinii appears to be restricted to small-crown forests on ultramafic substrates and highly localised in distribution. R. pairinii has been found only at 50-800 m, whereas R. hirsuta has been documented at 800-1600 m where they occur together in one locality, so there may be some kind of altitudinal segregation of the two species. This is reminiscent of R. gibbsiae and R. hepburnii, which show similar altitudinal segregation on Mt. Kinabalu (Dransfield 1983). The survival of rare species localised on specialised substrates, such as R. hirsuta and R. pairinii, needs to be carefully considered in conservation terms. They epitomize many rare and unique plants of the rain forest which require an intact undisturbed forest framework to survive. As forest habitats become increasingly fragmented by timber harvesting it will be necessary to preserve sizeable tracts of rain forest, particular on specialised sites such as those on ultramafic substrates, to conserve these special facets of the flora. ACKNO~DGEMENTS I thank S. Dransfield, Royal Botanic Gardens, Kew, for discussion and advice; J. Dransfield from the same institution for correcting the Latin diagnosis; C. Marsh and J. and E. Gasis of the Sabah Foundation for organizing the Mt Nicola expedition; and Datuk Miller Munang (Sabah's Director of Forestry) and V.F. Lee (Head, Forest Research Centre, Sepilok) for encouragement in studies of bamboos. The drawing of the new species here is the work of Martin Molubin of the Herbarium, Forest Research Centre, Sepilok. REFERENCES Dransfield, S. (1980) Three new Malesian species of Gramineae. Reinwardtia 9(4): 385 392. Dransfield, S. (1983) The genus Racemobambos (Gramineae: Bambusoideae). Kew Bulletin 37 (4): 661-679. 5 Holttum, R. E. (1956) Racemobambos, a new genus of bamboos. Gardens' Bulletin, Singapore 15 267-273. Kulip, J. (1992) Racemobambos glabra, a new record for Sabah. Sandakania. 1: 7-9. Wong, K. M, C.L. Chan and A. Phillipps (1988) The gregariousflowering of Miss Gibbs' bamboo (Racemobambos gibbsiae) and Hepburn's bamboo (R. hepburnii) on Mount Kinabalu, Sabah. Sabah Society Journal 8(4): 466-474. 6