A New Endemic Species of Trigonachras (Sapindaceae) from Sabah, Malaysia (Borneo)

Phytotaxa 88 (2): 19–24 (2013) ISSN 1179-3155 (print edition) www.mapress.com/phytotaxa/ PHYTOTAXA Copyright © 2013 Magnolia Press Article ISSN 1179-3163 (online edition) http://dx.doi.org/10.11646/phytotaxa.88.2.1

A new endemic species of Trigonachras (Sapindaceae) from Sabah, Malaysia (Borneo)

SVEN BUERKI1*, CHRISTOPHER DAVIDSON2, JOAN T. PEREIRA3 & MARTIN W. CALLMANDER4, 5 1Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, U.K. 2Idaho Botanical Research Foundation, 637 Warm Springs Ave., Boise, Idaho 83712, U.S.A. 3Forest Research Centre, Sabah Forestry Department, P.O. Box 1407, 90715 Sandakan, Sabah, Malaysia. 4Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, U.S.A. 5Conservatoire et Jardin botaniques de la ville de Genève, ch. de l’Impératrice 1, case postale 60, 1292 Chambésy, Switzerland *Corresponding author, email: [email protected]

Abstract

A new species of Trigonachras from Borneo is described and illustrated. Trigonachras postardanjeisin is endemic to the ultramafic soils of the Tawai Forest Reserve in Sabah, Malaysia (Borneo). It is morphologically close to the widespread Trigonachras acuta but differs by its glabrous inflorescence and infrutescence axes and fruits. The two species also differ by their ecology and distribution. Line drawings are provided for the new taxa, along with discussions of its morphological affinities and preliminary risk of extinction assessment. key words: new species, South-East Asia, taxonomy, ultramafic soil

Introduction

The Sapindaceae family (sensu Buerki et al. 2010, but slightly different from Acevedo-Rodríguez et al. 2011) is well diversified in Malesia with ca. 235 species classified into 42 genera, and constitutes an important element of the humid forests (Adema et al. 1994). The family is also important for the regional economy, including Dimocarpus longan Loureiro (1790: 233) and Nephelium lappaceum Linnaeus (1767: 125) (Adema et al. 1994). However, recent phylogenetic analyses based on plastid and nuclear DNA sequences have challenged the monophyly of several genera of Sapindaceae occurring in this area, e.g. Arytera Blume (1849: 169) and Cupaniopsis Radlkofer (1879a: 498) (Buerki et al. 2012a). This new evidence requires some additional taxonomic work to circumscribe generic delimitations within South-East Asian Sapindaceae. The authors, together with a team from the Sandakan Herbarium of the Sabah Forestry Department, have recently conducted fieldwork in Sabah, in the Malaysian part of Borneo, to expand their taxon sampling in Sapindacaeae and Pandanaceae by collecting genera and species not included in their previous phylogenetic analyses (see Buerki et al. 2009 for Sapindaceae; Buerki et al. 2012b for Pandanaceae). During this fieldwork, an unknown collection of a large and locally dominant flowering tree of Sapindaceae (Buerki et al. 338) was collected in the Tawai Forest Reserve (Bukit Tangkunan) growing on ultramafic soil (Fig. 1). Further observations conducted at the herbaria of Sandakan (SAN) and Singapore (SING) allowed matching this specimen with a fruiting collection from the same locality (Leopold & Amin SAN 75360) in the genus Trigonachras Radlkofer (1879b: 116) and previously described by Leenhouts as Trigonachras sp. nov. A. (Leenhouts 1988: 207). In his taxonomic treatment of the Malesian genus Trigonachras, Leenhouts (1988) recognized eight species and three additional morphological entities—these entities were not formally described due to the incomplete material, notably missing flowers. However, Leenhouts (1988) and Adema et

Accepted by Hans-Joachim Esser: 25 Feb. 2013; published online in PDF: 19 Mar. 2013 19 al. (1996) were able to easily discriminate all the species and morphological entities in a key based on vegetative and fertile characters which can still be used. The discovery of flowering material in Bukit Tangkunan allows to formally describe this new species as Trigonachras postardanjeisin Buerki & Callm. The new species is provided with a preliminary risk assessment based on the IUCN Red List Categories and Criteria (IUCN 2001), accompanied by line drawings, field photographs and a discussion of the morphological affinity of the new species with the closest member of the genus.

Trigonachras postardanjeisin Buerki & Callm., sp. nov. (Figs. 1–2)

Haec species Trigonachradi acutae Radlk. ample distributae arcte affinis, sed ab ea inflorescentiae infructescentiaeque axibus glabris (vs. trichomatibus fulvis indutis in T. acuta), fructu glabro (vs. brunneolo- vel in vivo rubello- tomentoso) atque sepalis abaxialiter puberulis adaxialiter parce pubescentibus (vs. utrinque trichomatibus brevibus sericeis satis dense indutis) facile distinguitur.

Type:—MALAYSIA. Borneo: Sabah: Bukit Tangkunan, Tawai Forest Reserve, Jalan Microwave road, 117˚12’28’’E, 5˚38’29’’N, 263 m, 9 April 2012 (fl.), Buerki, Callmander, Davidson, Christoph, Postar, Jeisin & Nur 338 (holotype MO!; isotypes G [G00368626]!, K!, L!, SAN!, SING!). = Trigonachras nov. sp. A fide Leenhouts (1988: 207).

Tree, 25–30 m tall, to 60 cm dbh, branches ca. 7 mm in diam. just below insertion of mature leaves, grey, glabrous. Leaves alternate, paripinnate, 14–26 cm long; petiole 4.5–5.5 cm long, ca. 2 mm in diam. at base, smooth, glabrous, enlarged at the base; leaflets (3–)5–7(–8) pairs, opposite to subopposite, blades concolorous, medium to dark green on both surfaces, subcoriaceous, stiff-pergamentaceous, elliptic to falcate, slightly asymmetric, 5–10 × 1.5–4 cm, glabrous on both surfaces, few domatia on lower surface, base strongly to distinctly oblique, acute, strongly attenuate, apex acute, margins slightly revolute; petiolules of largest leaflets (5–)8–12 mm long, 0.5–1 mm in diam., slightly enlarged at the base. Inflorescence pseudoterminal, 15–20 cm long, green, glabrous except the pedicels that are tomentose. Flowers, ca. 1 cm long, in glomerules of 2–4 flowers, evenly borne along the ultimate axes; bracts subtending the inflorescence axes caducous (not seen), leaving an evident scar; pedicels 3–6 mm long, tomentose, densely covered with whitish trichomes at base. Sepals 5, broadly-ovate, pale green in vivo, brown when dried, ca. 2 mm long, ca. 4 mm in diam (all sepals are equal in size), outside puberulent with whitish trichomes, inside sparsely hairy with whitish trichomes. Petals 5, long-clawed (blade enlarged distally), white, veined, ca. 2–3 mm long, ca. 1.5 mm in diam, outside glabrous, inside sparsely pubescent with whitish trichomes; scales 1–2, triangular, densely covered by a whitish indumentum, not crested. Disc circular, brown, ca. 2 mm in diam. Stamens 7–8, with filaments ca. 3–4 mm long at anthesis, densely pubescent in the proximal part, anthers yellow, ca. 1 mm long. Ovary globose, ca. 0.8 mm high, 1 mm in diam, densely velutinous, indument pale brown. Immature fruit 3- angular-obovoid, ca. (2–)2.5(–3) x 1–1.5 cm, narrowed to the base, apiculate, glabrous; wall somewhat fleshy, at least 1 mm thick, endocarp densely woolly. Distribution and habitat:—Trigonachras postardanjeisin is endemic to the lowland ultramafic forest in Bukit Tangkunan, Tawai Forest Reserve (Fig. 1). This species is particularly abundant along the road to the summit at elevations from 180 to 260 m. The most significant ultramafic sites in Sabah are Mt Silam, Bidu- Bidu hills, Mt Tawai, Morou Porou, Mt Tambuyukon, Hampuan and Kulung Hills, Pig Hill, Marai Parai and Meliau Range. Ultramafic substrates are found from sea level (islands such as Pulau Sakar near Lahad Datu) up to nearly 3,100 meters of elevation (at Mt. Kinabalu). Several species are endemic to this particular substrate throughout Sabah, e.g. Daemonorops serpentina Dransfield (1982: 810). Nevertheless, Trigonachras postardanjeisin is the only species that is currently restricted to Bukit Tangkunan, which is situated within the Tawai Forest Reserve.

Phenology:—Immature fruits have been collected in July and flowering material in April. Etymology:—The new species is named in honor of Postar Miun and Jeisin Jumian, both working at the Sandakan Herbarium of the Sabah Forestry Department. Postar and Jeisin greatly contributed to the success of the field work in various regions of Sabah and are immensely contributing to the knowledge and conservation of the flora of this region. Conservation status:—With an area of occupancy (AOO) of 9 km2, and one subpopulation, situated within a forest reserve (Bukit Tangkunan), Trigonachras postardanjeisin is assigned a preliminary status of Vulnerable (VU D2) based on the IUCN Red List Categories and Criteria (IUCN 2001) (calculation following Callmander et al. 2007). The Vulnerable Category is justified by the very restricted AOO that have a tendency to become Critically Endangered in a near future due to human activities or an unexpected event, e.g. fire. Additional specimens examined (paratypes):—MALAYSIA. Borneo: Sabah: 2 miles up the microwave station, 180 m, 26 July 1972, Leopold & Amin SAN 75360 (K, KEP, L, SAN!, SAR!, SING!). Discussion:—Trigonachras postardanjeisin is morphologically close to the widespread T. acuta (Hiern 1875: 677) Radlkofer (1879a: 672). The new species can, however, be easily discriminate by its glabrous inflorescence and infrutescence axes (pedicels are tomentose) and fruits (vs. fulvous indumentum on the inflorescence and infrutescence and brownish tomentum, reddish in vivo, on the fruit in T. acuta); sepals puberulent on the outside and sparsely hairy on the inside (vs. fairly dense short sericeous indumentum on both sides). Trigonachras postardanjeisin is endemic to ultramafic soil in Sabah and so far known only from Bukit Tangkunan, whereas T. acuta is often growing on sandy soils in Sumatra, Peninsular Malaysia and Borneo.

A NEW ENDEMIC SPECIES OF TRIGONACHRAS Phytotaxa 88 (2) © 2013 Magnolia Press • 21 FIGURE 2. Trigonachras postardanjeisin. A: immature fruit; B: stamen; C: branchlet with leaf and inflorescence; D: immature infrutescence; E: flower with detail of disc; F: flower with longitudinal section and details of petals and sepals. B, C, E, F from Buerki et al. 338 (G, L, MO); A, D from Leopold & Amin SAN 75360 (SING). Drawn by Roger Lala Andriamiarisoa.

We are grateful to Sharon Christoph and the team at the Sandakan Herbarium who accompany us in the field: Postar Miun, Jeisin Jumian, Nur Adillah binti Mohd, Yusof Brono Saludin and Junaidi Pokok, without their support this new species would not have been discovered. We would like to thank Dr Abdul Fatah Amir (Director, Sabah Biodiversity Centre) for facilitating the collecting permits in Sabah; Datuk Sam Mannan (Director, Sabah Forestry Department), Dr Lee Ying Fah (Head, Forest Research Center) and John B. Sugau (Curator, Sandakan Herbarium, Forest Research Centre) for their support in our research in Sabah; Mohmad Jumri Abdul Hamid for creating the distribution map and Roger Lala Andriamiarisoa for the fine illustrations. Finally we would like to thank Prof. Peter van Welzen and Dr Hajo Esser for their valuable comments that improved our manuscript. Financial support to SB was provided by Marie-Curie Intra-European Fellowship (CRADLE; no 253866); to MWC by a National Geography Exploration Grant (no 9042–11).

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