Ophiorrhiza hiepii L. Wu, Q. Gao & K.S. Nguyen, 2020

Liu, Wen-Jian, Gao, Qi, Nguyen, Khang Sinh, Nguyen, Dzu Van & Wu, Lei, 2020, Taxonomic studies on Ophiorrhiza in Vietnam I: Ophiorrhiza hiepii and O. hainanensis, a new species and new record from northern Vietnam, Phytotaxa 429 (1), pp. 65-72 : 66-70

Ophiorrhiza hiepii L. Wu, Q. Gao & K.S. Nguyen , sp. nov. ( Fig. 1 , 2 A-F)

Type: — VIETNAM. Tuyen Quang province: Na Hang District, 22°21′07.7″N, 105°25′24.5″E, alt. 255 m, stream sides or wet places on the slopes under the densely evergreen broad-leaved forest, 20 June 2018 (fl.), Lei Wu, Qi Gao, Su Juan Wei, Van Dzu Nguyen & Thinh, VN 0025 (holotype: CSFI [063690], isotypes: HN, more than ten duplicates).

Diagnosis: —Similar to Ophiorrhiza subrubescens Drake (1895: 215) in its heterostylous flowers, bract shape, corolla shape and indumentum inside the corolla, but differing in plant stature and branching (in O. hiepii up to 45 cm tall and usually unbranched vs. in O. subrubescens up to 80 cm tall and 3–5 or sometimes to 8-branched), number of secondary veins (5–8 pairs vs. 7–10 pairs), inflorescence structure (cyme umbelliform and sub-congested vs. racemose and comparatively lax), corolla tube length (8–10 mm long vs. 10–14 mm long) and length of stigma lobes of short-styled flowers (ca. 1.5 mm long vs. ca. 3 mm long).

Herbs, weak to sub-erect, to 45 cm tall; stems puberulent. Leaves usually in obviously unequal pairs; petiole 0.3–1.5 cm long, puberulent; blade drying papery, adaxially dark green to green, abaxially pale green, obovate-elliptic, elliptic or ovate, 2.2–9.5 × 1.8–3.8 cm, base cuneate to round, or sometimes truncated, margins entire, apex shortly acuminate, both surface glabrous, or abaxially pilosulous along principal veins; secondary veins 5–8 pairs; stipules usually persistent, broad ovate-triangular, apex acute, sparsely puberulent. Cyme umbelliform, terminal or sometimes axillary, drooping when young but sub-erect at anthesis, several to many flowered, sub-congested, puberulent; peduncles 2–3.5 cm, puberulent; bracts subulate, 2–5.5 mm long, puberulent. Flowers distylous, 5-merous. Calyx puberulent; hypanthium broadly compressed turbinate, 1.6–2.2 × 2.5–3 mm; lobes broadly triangular, to ca. 0.5 mm long. Corolla tubular, puberulent outside, tube 8–10 mm long, slender, slightly inflated at base; lobes elliptic-triangular, 2.8–3.2 × ca. 1.8 mm; stamens 5; stigmas bilobed. Long-styled form: corolla tube inside with a pubescent ring of long hair above the middle and puberulent above middle and onto lobes; anthers oblong, ca. 1.8 mm long, inserted near the middle of the corolla tubes; stigma positioned at the throat, lobes oblong, ca. 0.9 mm long. Short-styled form: corolla tube inside pubescent near the lower 1/3 and puberulent above middle and onto lobes; anthers linear narrowly oblong, ca. 2.0 mm long, positioned near the throat of the corolla tubes; stigma inserted a little below the middle of the corolla tubes, lobes lanceolate, ca. 1.5 mm long. Capsules obcordate, ca. 3–4.5 × 6–8.5 mm, puberulent. Seeds many, angular.

Phenology: —Flowers from March to June; fruits from April to possibly July.

Etymology: —The specific epithet is derived from the name of Dr. Nguyen Tien Hiep, the famous botanist of Vietnam, who has been devoted to the plant research and botanical conservation for Vietnam.

Conservation status: —Because no special exploration was carried out to study its distribution, this species was expectedly regarded as a plant meeting criteria of “data deficit” (DD) in terms of the IUCN Red list categories and criteria (2016).

Distribution and habitat: — Ophiorrhiza hiepii , is known so far from two populations, which are ca. 20 km away from each other by north-west direction, in Na Hang and Lam Binh Districts of Tuyen Quang Province, Northern Vietnam. The new species usually grows at an elevation of 250–400 m a.s.l., under the remnant primary evergreen broad-leaved forests on limestone mountains typically with Excentrodendron tonkinense (A.Chiev.) H.T.Chang & R.H.Miao , Garcinia spp , Rothmannia daweishanensis Y.M.Shui & W.H.Chen , Streblus ilicifolius (S.Vidal) Corner , Alphonsea tonkinensis A. DC. , Aspidistra spp. , Impatiens spp. , Begonia spp. , Strobilanthes spp. , Lysimachia baviensis C.M. Hu and L. insignis Hemsl.

Additional specimen examined (paratypes): — VIETNAM. Tuyen Quang province: Lam Binh District, Thuong Lam Commune, Deo But-Nhieu Lai route, at elevation of 350 m a.s.l., around point N 22°30′07″, E105°19′26″, 9 April 2019, Khang Sinh Nguyen et al. NSK 1224 ( CSFI, HN) ; Ibid , at elevation of 380 m a.s.l., around point N 22°30′10″, E105°19′16″, 9 April 2019, Khang Sinh Nguyen et al., NSK 1235 ( HN) .

Figures

FIGURE 1. Ophiorrhiza hiepii L. Wu, Q. Gao & K.S. Nguyen. A. Habit; B. Leaf, upper portion in adaxially view, lower portion in abaxially view. C. Stipule; D. Opened short-styled flower; E. Opened long-styled flowers; F. Infructescence in side view. Drawn from the holotype by Bi-Shan Li.

FIGURE 2. Ophiorrhiza hiepii L.Wu, Q. Gao & K.S. Nguyen.A.Habit; B. Flowers in side view; C. Inflorescencesin side view; D. Opened short-styled flower; E. Opened long-styled flowers; F. Infructescence in side view. O. subrubescens Drake. G. Habit; H. Inflorescences in side view; I. Opened short-styled flower; k. Opened long-styled. Scales: B, D, E=5 mm, C, F, H, I, K=1 cm. Photographed by L. Wu and K.S. NGUYEN.