Arenga plicata Mogea 2004

Abstract

1.17. Arenga plicata Mogea (2004: 186). Type:— INDONESIA, Sumatra, Prov. Jambi, District Kerinci, road from Penetai to Sungei Penuh, Kabupaten Sarko, lowland mixed dipterocarp forest, 300 m, 21 July 1972, Dransfield 2606 (holotype BO!; isotypes BH n.v., K![K000207888], L![L0042011, L0042010]). Plates 21 & 22. Stems clustered, number of stems per cluster not recorded, to 1.5 m tall, not swollen, ca. 3 cm diameter, bare; internodes 3–5 cm long; periderm smooth, color not recorded. Leaves number not recorded, paripinnate, to 3 by 0.4 m, distribution on the stem not recorded, erect to spreading; leaf sheaths ca. 20 cm long, disintegrating along the margins into a dark brown-black mass of thick fibers; ligules to 20 cm long; petioles slender, to 1.25 m long, 1 cm diameter, channelled in cross section, covered with brown indumentum; rachises ca. 1.4 m long, ca. 1 cm wide at the base, triangular in cross section, terete; petiolules absent; pinnae ca. 12 per side of the rachis, 25–40(60) by 3.5–10.5 cm, trullate, horizontal in 1 plane, regularly arranged along the rachis, proximal ones in groups of 2–4 and erect, conspicuously plicate at the base, gradually flattened through to the tips, adaxial surfaces dark green, abaxial surfaces white silvery with conspicuous stripes of dense brown indumentum especially in the distal part of the pinnae, lower two thirds or three quarters of the pinna with entire margins, distal part ± jagged, toothed, teeth to 1 mm long, blunt to pointed, not acuminate; apical pinna flabellate, 34–37 by 14–19 cm, apical margin with 3–5 points, sometimes none, densely toothed, teeth to 1 mm long Inflorescences unisexual, solitary, horizontal to erect, developing in an acropetal direction, to 4–6 by 3 cm; staminate inflorescences spicate; prophylls ca. 1.5 cm long; peduncular bracts 2–3, to ca. 20 cm long, covered with light brown indumentum; peduncles horizontal to slightly erect, 3–12 by 0.3–0.5 cm, rounded in cross section; rachilla 1 (spicate inflorescence), glabrous, color not recorded; staminate flowers ellipsoid in bud, ca. 6–8 by 2–2.5 mm; sepals 3, imbricate, broadly ellipsoid, margins irregular, with few notches to ca. 0.1–0.2 mm long, hairs 2 by 2.5 mm, color of outside surfaces not recorded; petals 3, valvate in bud, ellipsoid, 6–8 by 2–3 mm, coriaceous, outside surfaces color not recorded; stamens 30–40; filaments ca. 2.5–4 by 0.1 mm; anthers striate; pistillate inflorescences not recorded. Eophyll unknown. Distribution and habitat:— Sumatra (Jambi and Sumatera Barat) (Fig. 22) in lowland, mixed, primary, Dipterocarp forests at 300–950 m elevation. Reproductive biology:—Staminate flowers are at anthesis in June and July. Arenga plicata is pleonanthic with acropetal inflorescence development. Mogea (2004) considered this species to be dioecious. However, it is probable that it is similar to other acropetal species with unisexual inflorescences (A. obtusifolia, A. retroflorescens), and it is only a temporal dioecy (i.e., inflorescences of one sex are produced successively during a certain time and then the sex of the inflorescences changes). More observations are needed to better understand the reproductive behavior of this species. Arenga plicata is similar to A. retroflorescens particularly in its pleonanthic habit, temporal dioecy, conspicuous nodes, erect, spicate staminate inflorescences, and congested flower arrangement. Etymology:— plicata, meaning folded, in reference to the plicate bases of the pinnae. Preliminary IUCN conservation status:—Critically Endangered [CR] – Arenga plicata is endemic to Sumatra. Its area of occupancy AOO is estimated to be 8 km 2 (below the limits for Critically Endangered status under the criterion B2). The species is known from 2 “locations” (sensu IUCN 2012), exceeding the upper limit of the Critically Endangered status. Very little is known about this species throughout its range, and an important decline of its EOO and AOO can be predicted due to the important deforestation currently going on in Sumatra. Since the conditions for applying subcriteria a under criterion B1 and B2 are met, and considering the destruction of its habitat, the species is thus assigned a preliminary status of CR. In the event that Arenga talamauensis should be proved more abundant due to a better collecting effort, the present conservation status would be revised. Additional specimens examined:— SUMATRA. Sumatera Barat, Brani, 20 Jun 1918 (fl), Bünnemeyer, H. A. B. 3181 (BO!).

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