Elatostema hezhouense W.T.Wang, Y.G.Wei & A.K.Monro

Wei, Y. G., Monro, A. K. & Wang, W. T., 2011, Additions to the Flora of China: seven new species of Elatostema (Urticaceae) from the karst landscapes of Guangxi and Yunnan, Phytotaxa 29, pp. 1-27 : 7-10

Elatostema hezhouense W.T.Wang, Y.G.Wei & A.K.Monro , sp. no v. ( Fig. 4 & 5 ).

Elatostemo ichangensi similis sed nervis tertis vel quarternariis foliorum supra prominentiibus, foliis basi inaequilateris parte lata auriculata, pedunculato pistillato minori, inflorescentiis staminalis et pistillatis in cadem caule inserta, differt.

Type:— CHINA. Guangxi: Hezhou City, Etang Town, Guan Xin Yan Village , Dayan cave , growing in cave, N 24°20'54.0" E 111°31 ''23.7", 150 m, 15 March 2010, Y. G . Wei g1001 (holotype IBK, isotypes BM, PE) .

Perennial herb, epipetric, monoecious. Not tuber forming. Stems 300–520 × 1–2 mm, arching and or decumbent, succulent, green, drying drying finely sulcate, glabrous, younger stems with brown 4-celled glands, internodes 12–38 mm. Stipules solitary, opposite the leaf at each node, persistent, 4–6 mm, narrowly lanceolate to linear, glabrous. Leaves distichous, alternate, subequal, the major leaves petiolate, petioles 1.5– 2.0 × 0.75 mm, glabrous; laminae 55–115 × 20–25 mm, asymmatrically oblanceolate or falcate, subchartaceous to chartaceous, 5-nerved, the secondary nerves 4–6 pairs, 30–45° to the midrib; upper surface drying dark green (with a bluish hue when fresh), glabrous, cystoliths densely scattered, fusiform, 0.5 mm, tertiary and quarternary nerves raised and prominent; lower surface drying yellow-green, glabrous, sparsely brown glandular, cystoliths absent; base asymmetrical, auriculate/decurrent, auriculate/cuneate; margins serrate-dentate, the teeth spaced 4–7 mm apart; apex acuminate to caudate. Pistillate inflorescences borne on leafless basal portion of the stem, staminate inflorescences borne on leaf-bearing apical portion. Staminate inflorescences solitary, 5–8 mm, bearing 3–6 flowers in a pedunculate receptacle; peduncle 0.5–2.5 × 0.675 – 1.250 mm, glabrous, subtended by 2 unequal bracts; bracts unequal, major bract 3.5 mm, narrowly lanceolate, minor bract 1.5 mm, narrowly lanceolate to linear; receptacle 3.5–5.0 × 5–8 mm, oval, campanulate, 2-lobed or not lobed, glabrous, yellow-green above, green below, subtended by marginal bracts, the bracts unequal, borne opposite each other, pale green, glabrous; major bracts 2, 6– 7 mm, broad ovate, the apex corniculate, minor bracts 2, 3– 4 mm, ovate. Staminate flowers 2.0–2.5 × 2 mm immediately prior to anthesis, white, pedicellate, bracteolate; pedicel 1.5–2.0 mm, glabrous; bracteoles 2, equal, 2–3 mm, narrowly lanceolate or linear; tepals 4 or 5, the subapical appendage 1.0 mm, corniculate, green. Pistillate inflorescence solitary, 2.0– 2.5 mm, bearing 40 flowers in a pedunculate receptacle; peduncle 0.50–0.75 × 0.5 mm, glabrous, bracteate; bracts 0.375 mm, narrowly deltate; receptacle 1–2 × 2.5–4.0 mm, subquadrate, not lobed, glabrous, dark green above, dark green below, subtended by marginal bracts, the bracts unequal, dark green, ramentaceous, major bracts 2 or 4, 1.25–2.25 mm, ovate or bifurcate ovate, with a raised dorsal midrib, the apex corniculate, minor bracts 4 or 8, 0.75–1.00 mm, narrowly ovate or lanceolate, the apex corniculate. Pistillate flowers 0.50 × 0.25 mm at anthesis, cream, pedicellate; pedicel subsessile; bracteoles 2, equal, 0.30–1.25 mm, narrowly lanceolate or linear. Infructescences as pistillate inflorescences; achene 0.675 × 0.375 mm, oblongoid, with 8 narrow longitudinal ridges, pale brown.

Distribution:—Known only from the type locality in Hezhou County, Guangxi, Southwest China. Elatostema hezhouense is known only from a two-mouthed tunnel-like cave formed in limestone karst at an elevation of 150 m. This species grows close to the cave entrance in 7–9% daylight (photosynthetically active radiation).

Etymology:— Elatostema hezhouense is named after the type locality near Hezhou city.

Additional specimen examined (paratype):— CHINA. Guangxi: Hezhou City, Etang Town, Guan Xin Yan Village , Dayan cave , cave with two entrances in a low hillside, relatively light, N 24°20'54.0" E 111°31 ''23.7", 150 m, 23 May 2010, A. K . Monro & Y. G . Wei 6820 ( IBK, BM, MO, PE) .

Discussion:— Elatostema hezhouense is most similar to Elatostema ichangense Schroeter (1939) from which it can be distinguished based on leaf base and pistillate inflorescence morphology and the distribution of pistillate and staminate inflorescences as summarised in the table below:

Conservation status:—A Global Conservation Assessment is presented here based on IUCN methodology (2001, version 3.1). Elatostema hezhouense is known from a single locality (IUCN criteria D2). At this locality the population of this species comprises ca 20 mature individuals (IUCN criteria D1). Using the IUCN methodology our Global Conservation Assessment for E. hezhouense is Critically Endangered (CR) based on criteria D1 and D2: population size and number of locations combined with a plausible future threat that could drive this taxon to Extinct in a very short time. The cave locality is within a tree plantation and the cave is visited by local people recreationally. The use of this cave and distribution associated with the logging of the plantation represent plausible future threats.

Figures

FIGURE 4. Elatostema hezhouense. A. Habit with leaves, stipules and staminate inflorescences visible. B. Staminate inflorescence with marginal receptacle bracts. C. Staminate flower. D. Staminate bracteoles. E. Pistillate inflorescence viewed from below with marginal bracts visible. F. Pistillate flower and bracteole. Weig1001, IBK (Illustration by Sun Ying-Bao).

FIGURE 5. Elatostema hezhouense. A. Habitat, wall of two mouthed cave. B. Habit with leaves. C. Leaves with raised tertiary and quaternary nervation visible. Monro & Wei 6820 (Photo A.K. Monro).