Arenga longipes Mogea 2004

Abstract

1.10. Arenga longipes Mogea (2004: 182). Type:— INDONESIA, Sumatra, Prov. Bengkulu, District Rejang Lebong, beside the main road on km 18 from Kapahiang to Bengkulu, on the slope of mixed dipterocarp forest, 700 m, 25 August 1973, Dransfield 3585 (holotype BO!; isotype L![L0042004, L0042003, L0042005]). Stems loosely clustered, stoloniferous, with underground stolons ca. 50 cm long and ca. 0.5 cm diameter, number of stems per cluster not recorded, stems (when developed) to 25 cm tall, ca. 5 cm diameter; internodes ca. 3 cm long; periderm smooth, color not recorded. Leaves to 5 per stem, paripinnate, 250–300 by 60 cm, arising from the ground during the stemless phase, otherwise all along the stems, erect; leaf sheaths to 40 cm long, disintegrating along the margins into dark brown-black fibers; ligules to 10 cm long; petioles 50–250 cm long, 1–1.5 cm diameter, terete, glabrous to scarcely covered with brown indumentum; rachises 75–85 cm long, 1–1.5 cm wide at the base, rounded to ellipsoid in cross section; petiolules absent; pinnae to 16 per side of the rachis, 30–65 by 3–4.5 cm, linear, regularly arranged all along the rachis, proximal ones not clustered, horizontal, in 1 plane, concolorous, margins alternatively entire to toothed, teeth to 3 mm, not acuminate; apical pinna obtriangular, bifid, 4–5 pointed, 25 by 17 cm. Inflorescences bisexual, solitary, developing in a basipetal direction, to 130 by 5–8 cm, usually spicate or branched to 1 order; prophylls 3–15 cm long, tube-like; peduncular bracts 3, 10–30 cm long, 0.3–1.5 cm diameter, tube–like, covered with light brown indumentum; peduncles erect, to 110–115 cm long, 0.3 cm diameter, rounded in cross section; rachillae ca. 5, covered with sparse, light brown indumentum, color not recorded; flowers in triads, spirally arranged along the rachillae; staminate flowers falcate to sometimes ellipsoid, twisted at the tip in bud, 8–9 by 2–2.2 mm; sepals 3, imbricate, broadly ellipsoid, 2.5 by 3–3.2 mm, apical margin entire to scarcely notched, notch to 0.1 mm long, glabrous or sometimes few hair present on the margins, color not recorded; petals 3, valvate in bud, ellipsoid to obtriangular, twisted at the tip, 8–9 by 2–2.2 mm, coriaceous, color not recorded; stamens 10–12; filaments ca. 0.3–0.5 by 0.1 mm; anthers 4–5 by 0.8–1 mm, basifixed; pistillate flowers falcate to sometimes ellipsoid, twisted at the tip in bud, 6–7 by 1.5–2.2 mm; bracteoles 3, similar to the sepals; sepals 3, imbricate, broadly ellipsoid, 2.5 by 3–3.5 mm, apical margins entire to scarcely notched, notch to 0.1 mm long, color not recorded; petals 3, ellipsoid to obtriangular, not fused at the base, color not recorded; gynoecia elongate, 2.5 by 1–2 mm; locules 2; stigmas 2, sessile, triangular, blackish, to 1 mm long; staminodes 2–3, 0.8–1.2 mm long; fruits not recorded; seeds not recorded. Eophylls not recorded. Distribution and habitat:— Sumatra (Bengkulu) (Fig. 14) in disturbed mixed dipterocarp forests at 600–700 m elevation. It is known only from a small population very close to the Kapahiang-Bengkulu road at km 19-20. It was not found nearby in the Tabah Pananjung Nature Reserve. Sumatra has undergone under massive deforestation recently (Gaveau et al. 2007) and areas along roads are under even greater threat of being logged (Linkie et al. 2004). In addition, the size of the only known population is extremely limited. Taxonomic notes:—This species, still poorly known, exhibits some unusual characters in the Caryoteae, such as a stoloniferous habit, extremely long, terete inflorescences, and flowers organized in conspicuous triads (this also found in C. hastata). On the label of the type (Dransfield 3585), the field notes state “Extraordinary colonial stoloniferous Arenga ”. This species is in urgent need of protection, if it is not already extinct. Mogea (2004) cited four specimens in addition to the type. Unfortunately, none of these was available at BO when the first author visited in 2009. Arenga longipes has paripinnate leaves and concolorous leaflets, characters that are usually associated with Caryota rather than Arenga. Reproductive biology:— Arenga longipes is hapaxanthic with a basipetal inflorescence development. Stems develop only when sexual maturity is reached, as in A. longicarpa and A. porphyrocarpa. Dransfield in his field notes of the type specimen stated that at the anthesis the flowers smell like oil of wintergreen (Gaultheria sp.), which might have a pollinator attraction role. Etymology:— longipes, meaning long foot, perhaps in reference to the peduncle. Preliminary IUCN conservation status:—Critically Endangered [CR] – Arenga longipes is endemic to Sumatra. Its area of occupancy AOO is estimated to be 4 km 2 (below the limit for Critically Endangered status under the criterion B2). The species is known from 1 “location” (sensu IUCN 2012), equaling the upper limit for the Critically Endangered status. A. longipes is still fairly unknown and an important decline of its EOO and AOO can be predicted due to the important deforestation in Sumatra. Since the conditions for applying subcriteria a under criterion B1 and B2 are met the species is thus assigned a preliminary status of CR.

Authors 3

1. Marc Jeanson

   Muséum national d'Histoire naturelle · Institut de Systématique, Évolution, Biodiversité · New York Botanical Garden

   Affiliation as printed

   Center for Biodiversity & Evolution, The New York Botanical Garden, Bronx, NY 10458 - 5126, U. S. A. & Muséum National d'Histoire Naturelle, Département Systématique et Evolution, UMR 7205 Origine Structure et Evolution de la Biodiversité, 16 Rue Buffon, 75231 Paris cedex 05

2. Thomas L. P. Couvreur Aachen Botany Section

   Institut de Recherche pour le Développement · Université de Montpellier · Centre de Coopération Internationale en Recherche Agronomique pour le Développement · Diversité, adaptation et développement des plantes · Naturalis Biodiversity Center

   Affiliation as printed

   DIADE, Univ Montpellier, IRD, CIRAD, Montpellier, France https: // orcid. org / 0000 - 0002 - 8509 - 6587 & Naturalis Biodiversity Centre, Botany Section, Darwinweg 2, 2333 CR Leiden, The Netherlands

3. Andrew Henderson

   New York Botanical Garden

   Affiliation as printed

   Center for Biodiversity & Evolution, The New York Botanical Garden, Bronx, NY 10458 - 5126, U. S. A. & Center for Biodiversity & Evolution, The New York Botanical Garden, Bronx, NY 10458 - 5126, U. S. A. ahenderson @ nybg. org; https: // orcid. org / 0000 - 0001 - 6334 - 9435 & Center for Biodiversity & Evolution, The New York Botanical Garden, Bronx, NY 10458 - 5126, U. S. A