Ptilagrostis arcuata Z. S. Zhang & W. L. Chen, 2016

Zhang, Zhong-Shuai, Li, Ling-Lu & Chen, Wen-Li, 2016, A new species of Ptilagrostis (Stipeae, Poaceae) from Qinghai-Tibet Plateau, Phytotaxa 269 (3), pp. 231-235 : 232-235

Ptilagrostis arcuata Z. S. Zhang & W. L. Chen , sp. nov. ( Figs. 1 , 2 )

Diagnosis: — Ptilagrostis arcuata differs from P. concinna ( Hooker 1897: 230) Roshevitz (1934: 75) and P. junatovii Grubov (1955: 3) in its arcuate or heliciform awns usually with golden yellow or pale yellow hairs, narrower (0.2–0.3 mm) basal leaves, and the absence of bracts below the panicles.

Type: — CHINA. Yunnan: Dêqên, Bai-Ma mountain, 4366 m, 28°23.087′N, 99°00.398′E, 15 September 2014, Z. S. Zhang & L. L. Li 217 (holotype PE!).

Perennial herbs, tightly cespitose, not rhizomatous. Culms erect, glabrous, 15–60 cm tall, ca. 0.8–1.5 mm in diameter, with 2–4 nodes. Basal leaves filiform, ca. 0.2–0.3 mm wide. Leaf sheaths glabrous, longer than the internodes; ligules 0.8–2.1 mm long, margin complete, bifid or ciliate. Panicles contracted, 12–5 × 0.8–1.5 cm long, ovate or linear in outline, with 10–25 spikelets; branches 1–3 cm long, suberect, lowest branches without sheathing membranous bracts, lower branches usually paired, upper branches usually single; Spikelets purple or brownish, 5–6.6 mm long; glumes elliptic, 5–6.6 mm long, apex acute, vein 1, inconspicuous; lemmas 4.5–5.7 mm long, pilose below middle, scabrous above; apex 2–toothed, teeth 0.3–0.5 mm long; awns 0.9–1.3 cm long, arcuate or heliciform, plumose throughout; awns hairs golden yellow or pale yellow, in the lower part of the awns ca. 2 mm long, gradually decreasing to ca. 1 mm towards apex; paleas subequal to lemmas, 2–veined. Anthers 1.3–2 mm long, bearded or glabrous at apex.

Etymology: —The epithet arcuata refers to the unique curving awn. Chinese name: KĖǿffi̴

Comments:— Ptilagrostis arcuata is morphologically similar to P. concinna . Both species have contracted panicles with a few spikelets similar in size, but the new species has arcuate or heliciform awns usually with golden yellow or pale yellow awn hairs, narrower basal leaves (0.2 mm – 0.3 mm) and no bracts below the panicles ( Fig 2 : E, F, G). P. concinna has 1-geniculate awns usually with white or pale yellow hairs, broad basal leaves (0.3 mm – 0.8 mm) and usually (ca. 80%) has two obvious bracts below the panicles ( Fig 2 : J, K, L). Even among sympatric populations of these two species there are no morphological intermediates and we can separate them easily.

In addition, Ptilagrostis arcuata is also similar to P. junatovii in some morphological characters, such as contracted panicles with a few spikelets and similar sized spikelets. However P. arcuata has narrower basal leaves (0.2 mm – 0.3 mm) and heliciform and shorter (0.9–1.3 cm) awns, which differs from the broad basal leaves (0.3 mm – 0.8 mm), 1- geniculate and longer (1.4–2.0 cm) awns of P. junatovii . The main morphological differences among P. arcuata , P. concinna and P. junatovii are summarized in Table 1.

Distribution and habitat: — Ptilagrostis arcuata grows in alpine meadows, Rhododendron thickets or grassy mountain slopes, at about 3300–4400 m. It distributes in China: Sichuan, Yunnan, Xizang and also known in Nepal. On the other hand, P. concinna is common in Qinghai-Tibet Plateau and adjacent areas and P. junatovii distributes in Russia and Mongolia ( Tzvelev 1976).

Additional specimens examined: — CHINA. Sichuang: Litang , 4123 m, 24 September 2014, Z. S. Zhang & L. L. Li 323 ( PE!) ; 4058 m, 30°06.250′N, 100°05.056′E, 24 September 2014, Z. S. Zhang & L. L. Li 330 ( PE!) ; Integrated team of tropical biological resources in Yunnan 060 ( KUN!). Meigu , 3900 m, 27 July 1984, X. W. Tian 27 ( PE!). Xiangcheng, 4400 m, 16 August 1973, Sichuan Veget. Exped. ( PE!). Yunnan: Shangri-La, 3770 m, 7 August 1981, X. W. Tian & Z. H. Zhang 27 ( PE!) ; 3924 m, 27°24.289′N, 99°47.217′E, 22 September 2014, Z. S. Zhang & L. L. Li 311 ( PE!) . NEPAL. Langtang , 4130 m, 15 September 1986, G. Miehe & S. Miehe 842 ( K!) .

Cytology: —The chromosome number of Ptilagrostis arcuata is 2 n =22, the same as other species of Ptilagrostis ( Tzvelev 1976) . This new species has only medium and small chromosomes and the length of chromosomes varies from 1.9 μm to 3.6 μm long. The karyotype is 2 n =22= 14m +6sm+2st ( Fig. 2 , m: metacentric chromosome; sm: submetacentric chromosome; st: acrocentric chromosome).

Figures

FIGURE 1. Ptilagrostis arcuata. A. habit; B. ligule; C. base of the panicle (without bract); D. spikelet; E. glume; F. lower glume; G. upper glume; H. floret. Drawn by Ms. Zhi-Juan Chen based on the type (Z. S. Zhang & L. L. Li 217).

FIGURE 2. Ptilagrostis arcuata: A–B. habitat; C. habit; D. panicle; E. basal leaves; F. base of panicle (without bracts); G. floret (arcuate awn); R. chromosomes; S. karyotype. P. concinna: H. habit; I. panicle; J. basal leaves; K. base of panicle (with membranous bracts); L. floret (unigeniculate awn); P. junatovii: M. habit; N. panicle; O. basal leaves; P. base of panicle (without bracts); Q. floret (unigeniculate awn). Bars in G, L, Q represent 5 mm; in E, J, O represent 1 mm; in R, S represent 5 μm.