Achnatherum pilosum Z.S. Zhang & W.L. Chen, 2018

Zhang, Zhong-Shuai, Jiang, Shan-Wen & Chen, Wen-Li, 2018, Achnatherum pilosum (Stipeae, Poaceae), a new species from Qinghai-Tibet Plateau, Phytotaxa 350 (1), pp. 86-92 : 87-91

Achnatherum pilosum Z.S. Zhang & W.L. Chen , sp. nov. ( Fig.s. 1–2 )

Achnatherum pilosum resembles A. inebrians ( Hance 1876: 212) Keng ex Tzvelev (1968: 40) , A. psilantherum Keng ex Tzvelev (1968: 41) , A. inaequiglume Keng (1976: 151 , 443), and A. saposhnikovii ( Roshevitz 1916: 174) Nevski (1937: 224) by having ligules truncate, panicles contracted or loosely contracted, lemmas similar in length (2.5–4.5 mm long), and calluses 0.2–0.3 mm long, bearded. It differs from them by the combination of panicles loosely contracted; glumes subequal, 5.5–7 mm long; lemmas 2.8–3.2 mm long, evenly pubescent with some slightly long hairs (ca. 0.6 mm long) at the apex; awns 1 - or inconspicuously 2 - geniculate, 0.9–1.5 cm long, scabrous, with twisted columns; and anthers 1.5–1.8 mm long, bearded at the apex.

Type: — CHINA. Sichuan: Dêgê, Chola Shan, alt. 3200 m, 31.82°N, 98.58°E, 14 September 2017, Zhang 2379 (holotype PE!).

Plants tightly cespitose, not rhizomatous, basal branching extravaginal. Culms erect, glabrous, 40–80 cm tall, 0.5–1.3 mm diam., with approx. 3 nodes. Leaves basal, except in the flowering culms; leaf sheaths glabrous, shorter than the internodes; ligules 0.1–0.9 mm long, truncate, often toothed; leaf blades 8–23 cm × 0.3–3 mm, filiform, flat or folded. Panicles 7–11 × ca. 1 cm, loosely contracted, narrowly oblong or linear; branches 2 to 4 per node, suberect or slightly spreading, up to 4 cm long. Spikelets 5.5–7 mm long, yellowish - brown or purple and hyaline towards the apex; glumes subequal or the lower glume slightly longer than the upper glume by 1 mm, lanceolate, 3 - veined, apex acute to acuminate; floret fusiform; lemma 2.8–3.2 mm long, evenly pubescent on the back, hairs ca. 0.6 mm at the apex and ca. 0.5 mm long below, apex with two lobes ca. 0.1 mm long; awn 0.9–1.5 cm long, persistent, 1 - or inconspicuously 2 - geniculate, scabrid, column twisted; callus ca. 0.3 mm long, subacute; palea slightly shorter than the lemma; anthers three, 1.5–1.8 mm long, bearded at the apex. Caryopsis 2.5–3 mm long, obovate, distal portion slightly exposed between gaping lemma and palea or concealed by floret at maturity.

Etymology: —The specific epithet ‘pilosum’, from the Latin word ‘pilus’ ( Clifford & Bostock 2007), refers to the anthers bearded at the apex. Chinese name: ḂIȐȐḍ.

Comments: —The new species was included in Achnatherum because of the fusiform spikelets ( Fig. 1C–D , 2D ); subacute calluses; lemmas with non - overlapping margins ( Fig. 1F, G ); and awns persistent, twisted, 1 - or inconspicuously 2 - geniculate ( Fig. 1D , 2D, I ), which are the diagnostic features of this genus ( Romaschenko et al. 2012, Kellogg 2015). In addition, its placement in Achnatherum is also supported by the maize - like lemma epidermal pattern ( Fig. 2S ) and chromosome number 2 n = 24 ( Fig. 2T ) ( Romaschenko et al. 2012, Kellogg 2015).

Achnatherum pilosum is morphologically similar to A. inaequiglume , A. inebrians , A. psilantherum , and A. saposhnikovii , which have truncate ligules, contracted panicles ( Fig 2C ), lemmas similar in length (2.5–4.5 mm long; Fig 2D–M ), and calluses 2–3 mm long, bearded ( Fig 2I–M ) ( Hooker 1896, Bor 1960, Tzvelev 1976, Freitag 1985, Noltie & Garden 2000, Wu & Phillips 2006). Achnatherum inaequiglume and A. saposhnikovii differ from A. pilosum due to their straight, not twisted awns, and anthers glabrous at the apex ( Fig. 2E, J, O and H, M, R respectively), whereas the new species presents 1(–2)-geniculate, twisted awns, and anthers bearded at the apex ( Fig. 2D, I, N ). The former presents unequal glumes ( Fig. 2E ), long awns (1.5–2 cm long) and long hairs (3–4 mm long) at the apex of the lemma ( Fig. 2E, J ), whereas the second presents subequal glumes ( Fig. 2H ), short awns (0.4 cm long) and lemmas evenly pubescent ( Fig. 2H, M ). The new species differs from A. inebrians by the loosely contracted panicles ( Fig. 2C ), short lemmas (2.8–3.1 mm long), shorter hairs at the apex of the lemmas (ca. 0.6 mm long), long awns (0.9–1.5 cm long) and shorter anthers (1.5–1.8 mm long). The new species differs from A. psilantherum by its short glumes (5.5–7 mm long), lemmas (2.8–3.1 mm long), awns (0.9–1.5 cm long), and short anthers (1.5–1.8 mm long) with a cluster of beard at the apex ( Fig. 2N ). Morphological differences among A. pilosum and relatives are summarized in Table 1.

Distribution and habitat: — Achnatherum pilosum grows in forest fringes, grassy mountain slopes and wet river banks ( Fig. 2A–B ). It is endemic to China, restricted to Sichuan and Qinghai provinces ( Fig. 3 ). Achnatherum inebrians is widely distributed in Qinghai - Tibet plateau and central Asia ( Tzvelev 1976, Wu & Phillips 2006). Achnatherum inaequiglume and A. psilantherum occur in the northeast and adjacent areas of Qinghai-Tibet plateau and their distribution area do not overlap with that of the new species ( Tzvelev 1976, Wu & Phillips 2006). Achnatherum saposhnikovii is distributed in central Asia, which is also geographically isolated from the new species ( Tzvelev 1976, Wu & Phillips 2006).

Lemma epidermal pattern: — Achnatherum pilosum presents a MLP, typical of Achnatherum s.s. ( Romaschenko et al. 2012). The FC are thin - walled, approximately equal in length and width to significantly shorter than wide ( Fig. 2S ). The FC are square - round, or longitudinally compressed ( Fig. 2S ). Oval silica bodies regularly alternate with FC ( Fig. 2S ). Lemma surface resembles the surface of a fruiting inflorescence of maize ( Fig. 2S ). Cork cells are absent. Macrohairs are present ( Fig. 2S ).

Cytology: —The diploid chromosome number of Achnatherum pilosum is 2n = 24 ( Fig. 2T ), as well as that of A. calamagrostis ( Linnaeus 1759: 872) Palisot de Beauvois (1812: 146) , type species of Achnatherum , and most species of Achnatherum s.s. ( Tzvelev 1976, Martinovský 1980, Vázquez & Devesa 1996, Romaschenko et al. 2012).

Additional specimens examined (paratypes): — CHINA. Qinghai: Nangqên , 3650 m, 32.32°N, 96.47°E, 4 September 1996, Ho, et al. 2898 ( PE!) ; Chindu xian, 3700 m, 32.98°N, 97.35°E, 15 August 1996, Ho, et al. 1828 ( PE!) .

Figures

FIGURE 1. Achnatherum pilosum: A. Habit; B. Ligule; C. Glumes; D. Floret; E. Lemma, dorsal view; F. Floret, lateral view; G. Lemma, ventral view; H. Palea, dorsal view; I. Palea, ventral view; J. Lodicules; K. Anthers; L. Caryopsis, dorsal view, showing the embryo. Scale bars: A = 1 cm; B–L = 1 mm. Drawn by Mr. Zhong-Shuai Zhang (based on Zhang 2379).

FIGURE 2. Achnatherum pilosum (Zhang 2379, PE): A. Habitat; B. Habit; C. Panicles of A. pilosum, A. inaequiglume, A. inebrians, A. psilantherum, and A. saposhnikovii (from left to right); D. Glumes and floret; I. Lemma and proximal part of the awn; N. Anthers; S. Lemma epidermal pattern, scanning electron microscope micrograph; T. Chromosome number, mitotic metaphase. A. inaequiglume (Zhang 1303, PE): E. Glumes and floret; J. Lemma and proximal part of the awn; O. Anthers; A. inebrians (Zhang 2353, PE): F. Glumes and floret; K. Lemma and proximal part of the awn; P. Anthers; A. psilantherum (Zhang 2509, PE): G. Glumes and floret; L. Lemma and proximal part of the awn; Q. Anthers; A. saposhnikovii (Zhang 347, PE): H. Glumes and floret; M. Lemma and proximal part of the awn; R. Anthers. Scale bars: C = 5 cm; D–M = 2 mm; N–R = 1 mm; S = 10 μm; T = 5 μm.

FIGURE 3. Distribution map of Achnatherum pilosum.