A New Leptochloa (Poaceae: Chloridoideae) from Papua New Guinea and the Torres Strait Islands of Australia

Abstract

Leptochloa simoniana N. Snow is newly described from Papua New Guinea and Boigu Island in the Torres Strait, Queensland, Australia. A key and tabular diagnosis are provided for L. simoniana and morphologically similar congeneric species. It most resembles the sub-Saharan species L. coerulescens. Its chief diagnostic features are the long-sericeous to arachnose hairs at the apex of the callus and the densely scabrous adaxial and abaxial leaf surfaces. The species is currently known from only three sites and is thus considered vulnerable. RESUMEN. Se describe Leptochloa simoniana N. Snow, una especie nueva de Paptia Nueva Guinea y de la Isla Boigu en el Estrecho de Torres, Queensland, Australia. Se proporcionan una clave y una diagnosis tabular para L. simoniana y especies congendricas morfol6gicamente similares. Es muy parecida a L. coerulescens, una especie del sub-Sahara. Se distingue principalmente por los tricomas largos a aracnoideos en la base de la lema. En actualidad la especie se conoce s61o de tres lugares y por lo tanto se la considera vulnerable. The eragrostoid genus Leptochloa P. Beauvois occurs worldwide from temperate to tropical regions and consists of some 40 taxa (Snow, 1997a, 1998a). All widespread annual species are considered weedy in agricultural situations (Hafliger & Scholz, 1981; Snow, 1997a), and some are anthropogenically transcending oceanic boundaries and becoming established on continents far beyond their normal range (Lazarides, 1980; Snow & Simon, 1999). This article describes a new species brought to my attention by the collector of the type material, Barbara Waterhouse, and brings to three the number of newly described species in the genus since 1997 (Snow & Simon, 1997; Snow, 1998b). Morphological attributes of herbarium material were measured and compared to known species of Leptochloa following Snow (1997a) under a phylogenetic species concept (Snow, 1997b). Descriptive terminology follows recommendations of the Systematics Association Committee (1962). Leptochloa simoniana N. Snow, sp. nov. TYPE: Australia. Queensland: Cook District, Boigu Island, Torres Strait, 9o13.89'S, 142'13.26'E, 31 Mar. 1998, B. M. Waterhouse & J. F Grimshaw BMW 4862 (holotype, BRI; isotypes, BO, BRI, CANB, GREE, K, L, LAE, MEL, MO, NAQS, NSW, QRS). Figure 1. Similis Leptochloae caerulerti autem paniculae ramis pluribus, pilis arachnoideis lemmatis basi, lemmatibus glumisque longioribus, vaginis dense scabris interdum pilos tuberculatos pilosos gerentibus, differt. Plants annual, caespitose. Culms erect, sometimes branching, arising from fibrous roots, 90-140 cm tall, 2.5-4.0 mm wide at base, round to laterally compressed; nodes glabrous but often glaucous; internodes glabrous, 6-20 cm long, hollow. Leaf sheaths somewhat flattened near ground, longer or shorter than internodes, prickles short but dense throughout, tuberculate pilose hairs sometimes present, margins glabrous; collars green, lacking anthocyanin pigmentation. Ligules membranous, 3-4 mm long, apex truncate and erose. Leaf blades + linear, 20-35 x 0.35-0.9 cm at base, densely scabrous throughout above and below, occasionally bearing a few tuberculate pilose hairs, flat but drying involute, remaining attached at base, midrib prominent above near base, less so elsewhere. Panicles narrow, inserted basally, exserted ca. 2/3 length or more, 45-75 x 2--10 cm; branches 6575, alternate or sub-whorled, ascending to steeply ascending, 5-10 cm long near base decreasing to 5 mm or less near apex, rigid to slightly flexuous, densely scabrous throughout and highly striate, axils glabrous. Spikelets 3(4)-flowered, laterally compressed, 3.0-3.4 mm long, imbricate ca. 1/5-1/2 their length, pedicels 0.5-1.0(-2.0) mm long. Glumes membranous, 1-nerved, narrowly triangular to narrowly ovate; lower glume 1.6-2.1 mm long, apex attenuate, scabrous with prickles on midnerve and sometimes laterally; upper glume 1.8-2.4 mm long, apex acute to attenuate and sometimes shortly mucronate, scabrous with prickles on midnerve and laterally. Lemmas 3-nerved, membranous, (lowermost) 2.3-2.7 mm long, ovate, green, sometimes tinged maroon or crimson, lateral nerves neither prominent nor distinctly raised abaxially, hairs sericeous to arachnose at very base and callus apex (up to 1.3 mm long) but becoming relatively short sericeous (< 0.5 mm long) apically along nerves (sometimes sparsely so), sometimes shortly sericeous between nerves in lower third, hair tips tapered (Snow, 1996); apex acute or slightly emarginate and sometimes shortly mucronate. Palea thinly membranous, subequal to ca. 2/3 lemmatal length, narrowly elliptic to narrowly ovate, sericeous to arachnose along nerves; apex obtuse or NovoN 10: 238-241. 2000. This content downloaded from 157.55.39.255 on Tue, 24 May 2016 05:30:40 UTC All use subject to http://about.jstor.org/terms