Elatostema yachense W.T.Wang, Y.G.Wei & A.K.Monro, 2011

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 : 23-26

Elatostema yachense W.T.Wang, Y.G.Wei & A.K.Monro , sp. nov. ( Fig. 14 & 15 )

Elatostemo sinensi var. xinningensi similis, sed plantis monoeciis, foliis glabris marginem ad apicem crenatis, stipulis minoribus, bractis principalibus receptaculi staminalis et bracteolis staminalibus majoribus, differt.

Type:— CHINA. Guangxi: Longlin County, Yacha Town, Dahongbao nature reserve , 25°53’34”N, 105°11’03”E, 1000–1200 m (coordinates and altitude taken from Google Earth), 27 March 2009, Y. G . Wei 087 (holotype IBK, isotypes BM, MO, PE) .

Perennial herb, terrestrial, monoecious. Not tuber forming. Stems 200–380 × 1.50–1.75 mm, erect or decumbent, smooth, succulent, green-brown or brown, glabrous, internodes 6–35 mm. Stipules 2 at each node, one interpetiolar, one intrapetiolar, persistent, 1.5–2.5 mm, lanceolate, glabrous. Leaves distichous, alternate, terminal pair of leaves subopposite, subsequent leaves unequal, the major leaves subsessile, petioles 0.5–2.0 × 0.50–0.75 mm, glabrous; the major laminae 35–95 × 9–22 mm, length:width ratio 1:3.6–4.0, asymmetrically oblanceolate, weakly falcate or oblanceolate/elliptic, subchartaceous, 3-nerved, the secondary nerves 2 or 3 pairs, 45–60° to the midrib; upper surface drying green-brown, glabrous, cystoliths densely scattered, fusiform, 0.675 mm; lower surface drying olive green, glabrous, cystoliths absent but imprint of upper surface cystoliths visible; base asymmetrical, cordate or cordate/obtuse; margins asymmetrically crenate, the teeth spaced 4–5 mm apart; apex cuspidate to acuminate. Staminate and pistillate inflorescences borne on the same stem. Staminate inflorescences solitary, 8–10 mm, bearing 6–10 flowers in a pedunculate receptacle; peduncle 1–2 × 0.75 mm, glabrous, subtended by a bract; bract 1.25 mm, narrowly ovate; receptacle 7–9 × 10–13 mm, campanulate, not lobed, glabrous, pale green above, pale green below, subtended by marginal bracts, the bracts unequal, marginal, major bracts opposite to each other, submajor bracts perpendicular to major bracts, pale green, major bracts 2, 6– 8 mm, narrowly lanceolate, fused together at their base, submajor bracts 4, 7 mm, narrowly lanceolate. Staminate flowers 3–5 × 2.5 mm immediately prior to anthesis, white, green towards the apex, pedicellate, bracteolate; pedicel 4–6 mm, glabrous; bracteoles 2, unequal, major bracteoles 4–5 mm, minor bracteoles 1.5–2.0 mm, major bracteoles very narrowly lanceolate to linear, minor bracteoles linear, both pubescent; tepals 5, the subapical appendage 1.00– 1.25 mm, corniculate. Pistillate inflorescence solitary, 3.5–4.0 mm, bearing 40–60 flowers in a pedunculate receptacle; peduncle 2 × 0.375 mm, glabrous, ebracteate?; receptacle 2.5–3.0 × 4 mm, sub quadrate ot trapeziform, not lobed, glabrous, yellow-green above, green below, subtended by marginal bracts, the bracts unequal, major bracts 2, 2.0– 2.5 mm, broad ovate to suborbicular the apex corniculate, submajor bracts 8, 1.75–2.00 mm, oblong-elliptic or lanceolate, the apex corniculate and thickened. Pistillate flowers 0.375 –0.675 × 0.250 – 0.375 mm at anthesis, cream, pedicellate; pedicel 0.125 mm; bracteoles 2, unequal, major bracteole 2.5–3.0 mm, linear, pubescent, minor bracteole 1.0– 1.5 mm, obovate with a corniculate supapical dorsal appendage. Infructescences not seen.

Distribution:—Known only from the type locality, the Dahongbao nature reserve in Longlin County, Guangxi. The vegetation is composed of evergreen and deciduous broadleaf forest on limestone.

Etymology:— Elatostema yachense is named after the town from where the type was collected.

Discussion:— Elatostema yachense is most similar to Elatostema sinense var. xinningense (W.T.Wang) L.D.Duan & Q.Lin ( Wang 1985) from which it can be distinguished based on sexual system, leaf, stipule, staminate receptacle and flower morphology as summarised in the table below:

Conservation status:—A Global Conservation Assessment is presented here based on IUCN methodology (2001, version 3.1). Elatostema yachense is known from a single locality (IUCN criteria D2). At this locality the population of this species comprises ca 300 individuals (IUCN criteria D1) growing in three populations within a nature reserve. Using the IUCN methodology the Conservation Assessment for E. yachense would be Vulnerable (VU), however no plausible threat that could be found to confirm this status as the population is located within a protected area and not under threat in the near future. For this reason our Global Conservation Assessment for Elatostema yachense is Near Threatened (NT).

Figures

FIGURE 14. Elatostema yachense. A. Habit with stipules, staminate and pistillate inflorescences visible. B. Staminate inflorescence with receptacle bracts, bracteoles and flowers visible. C. Major staminate bracteoles. D. Staminate flower with subapical tepal appendages and stamens visible. E. Pistillate inflorescence viewed from below with marginal receptacle bracts visible. F. Pistillate flower, minor receptacle bract and bracteoles. Weig087, IBK (Illustration by Sun Ying-Bao).

FIGURE 15. Elatostema yachense. A. Habit. B. Staminate inflorescence with major receptacle bracts. C. Staminate flowers. D. Pistillate inflorescences with a young staminate inflorescence in the foreground. Wei g087 (Photo Y.G. Wei).