Bistorta tenuifolia (Hsien Wu Kung) Futoshi Miyamoto & Hideaki Ohba (2005: 280) var. tenuifolia

Rai, Ishwari Datt, Singh, Gajendra & Rawat, Gopal Singh, 2013, Bistorta tenuifolia var. gidarensis (Polygonaceae), a new variety from India, Phytotaxa 92 (1), pp. 13-19 : 14-18

Bistorta tenuifolia (Hsien Wu Kung) Futoshi Miyamoto & Hideaki Ohba (2005: 280) var. tenuifolia

Bas.: Polygonum tenuifolium Hsien Wu Kung (1935: 367) . Type :— CHINA: Shensi , Near Pahsiantai Taipaishan, 3700 m, 5 August 1933, Wang W1846 (holotype PE!) .

Bistorta tenuifolia (H. W. Kung) Miyam. & H. Ohba var. gidarensis I.D. Rai, G. Singh & G.S. Rawat , var. nov. Type:— INDIA. Uttarakhand: Uttarkashi, Gidara alpine meadow, 3852 m, 30°56'13.20"N, 78°36'16.48"E, 28 June 2010,

Rai et al. 11543 ( holotype WII!) .

Diagnosis: — Bistorta tenuifolia var. gidarensis differs from B. tenuifolia in having the perianth lobes with acute apex, smaller stamens included in the perianth and monothecous reniform anthers.

Description: —Herb perennial (root stock), 5–20 cm high. Stem simple or in pair, erect or nearly so, pale green to green coloured; rhizome dark-brown, swollen, bulbous, covered with old leaf sheaths. Basal leaves 4–6, petioled (petiole 1.5–6 cm long), linear (2–15 × 0.1–0.2 cm) with acute apex, base narrowly decurrent, margin entire and revolute, upper surface glabrous, lower surface minutely hairy or glabrous, pale green; stipules 2–5 mm long, membranaceous, brown with acute apex; ocrea 1–3 cm long; cauline leaves 2–3, sessile, linear (2–4.5 cm long), apex acute, base narrowly decurrent, margin entire and revolute. Inflorescence in solitary cylindric raceme, 1.5–5 cm long; flowers white, solitary, with peduncle pale green to light brown (1.5–2.5 mm long); bracts (1.3–3 × 0.3–0.6 mm) lanceolate to oblong, membranous, apex acuminate to acute, pale brown; bracteoles (1–1.5 mm) membranous, lanceolate, apex acute; tepals 5 (1.7–2.2 mm long), oblong to oblanceolate, apex acute; stamens 8 with white filaments (0.5–1 mm long) and brown anthers (0.2–0.3 × 0.1–0.15 mm); brown coloured nectary glands at base of the stamen; pistil 2–4 mm long, styles 3 (1.5–3 mm long) white, connate at base, stigma capitate, brown, ovary trigonous to globose (0.5–1.25 mm long) narrowly lobed, dark-red to dark-pink; bulbil green to purple, 1.5–2.5 mm long, covered by bract and bracteoles; bulbil begin the develop from the basal part of the inflorescence before of the flowering; fruits and seeds unknown ( Figs 1 and 2 ).

Ecology: — B. tenuifolia var. gidarensis grows on alpine meadows (especially along stream sides, mountain slopes in silty-loam soil) between 3600–4200 m a.s.l. The taxon occupied small areas (less than 15 sqm). The climate of the study area is characterized by three seasons: a short summer (May to June), monsoon (July to September) and prolonged winter (October to April, with a snowy covering of about five months), with temperature ranges between 25 ° C in summer and -15 ° C in winter. Flowering time is from June to August. The two varieties occur in different climatic conditions. Latitude, altitude and continental mass effect are the most influencing factors regulating the climatic attributes in the distribution area of these varieties across the Himalayan mountains and China. Due to the unique directions of monsoon from the Bay of Bengal and the Arabian Sea, Central Himalaya region (for var. tenuifolia ) area is characterized by a continuous wet condition of the climate, while Western Himalaya (for var. gidarensis ) remains comparatively drier due to delayed rainfall during summer.

Etymology: —The epithet gidarensis come from the Gidara alpine meadow in Uttarakhand.

Taxonomical notes: —The new variety mainly differs from B. tenuifolia s. s. in having perianth lobes with acute or acuminate apex (rounded in the nominal variety) and stamens 0.5–1 mm long (stamens 2–2.5 mm long in the nominal variety), included in the perianth and less than half of the total length of the perianth (exserted in the nominal variety). The presence of small dark red coloured ovary and long styles are also differences (see Table 1). The two varieties are allopatric [ var. gidarensis from Western Himalaya, var. tenuifolia from Central Himalaya ( Nepal) and China] which are distributed in different climatic conditions.

Conservation status: —The variety occurs in three localities in the Western Himalaya. Due to the peculiar habitat, the population is small (about 200 individuals). Three scattered population can be osbserved: the first one of about 40 individuals from Gidara, a second population of 10 individuals from Kanasar, and the third one of 150 individuals from GHNP. A strong anthropogenic impact (in the form of high grazing pressure), existing in the first two localities, might cause the decline or a local extinction of the taxon. On the basis of the IUCN Red List categories and criteria ( IUCN 2011) the variety is evaluated as endangered (EN, D).

Additional Specimens examined:— Nepal: Miyamoto & al. 20210059, 20210045, 20210101 (2002, TI) ; China: T. P . Wang W1846 (1933, PE) , T. T . Yu 12126, (1937, PE), Chen & al. 8167 (1884, PE), T. N . Liou & P. C . Tsoong 2899 (1939, PE) ; India: Uttarkashi district ( Gidara , 3852 m, 30°56'13.20"N, 78°36'16.48"E; Kanasar, 3834 m, 30°53'41.41"N, 78°28'13.12"E) , Uttarakhand and Great Himalayan National Park ( Dhela , 3610 m, 31°45'26.62"N, 77°27'40.42"E) , Himachal Pradesh.

Figures

FIGURE 1. Bistorta tenuifolia var. gidarensis I. D. Rai, G. Singh and G. S. Rawat: A. Habit. B. Flowering branch. C. Flower. D. Perianth lobes with stamen. E. Pistil and androecium. F. Bulbils.

FIGURE 2. Bistorta tenuifolia var. gidarensis I.D. Rai, G. Singh and G.S. Rawat: A. Habit. B. Flowering branch. C. Flower. D. Perianth lobes with pistil. E. Perianth and androecium (brown spots). F. Perianth. G. Pistil and androecium. H. Bulbils.