Elatostema laevicaule W.T. Wang, A.K. Monro & Y.G. Wei, 2013

Wei, Yi-Gang, Monro, A. K. & Wang, Wen-Tsai, 2013, Additions to the Flora of China: three new species of Elatostema (Urticaceae) from Guangxi, Phytotaxa 147 (1), pp. 1-12 : 2-4

Elatostema laevicaule W.T. Wang, A.K. Monro & Y.G. Wei , sp. nov. ( Fig. 1A–C )

Most similar to Elatostema filipes from which it can be distinguished by the length and shape of the stipules, the number and shape of the bracts subtending the staminate receptacle and the shape of the staminate bracteoles.

Type:— CHINA. Guangxi: Napo county, Laohutiao nature reserve , limestone hills growing under small trees and shrubs, N 23°05′51″ E 105°48′39″, 1100 m, 10 March 2009, Y. G. Wei g043, (holotype PE!, isotype IBK!). Figure 2A–C

Perennial herb, terrestrial, dioecious? Not tuber forming. Stems ca 280 x ca 3 mm, erect, branched, green when fresh, furfuraceous, glabrous, sulcate, cystoliths sparsely scattered, bacilliform, 0.2–0.3 mm, internodes 7–18 mm. Stipules 2 at each node, caducous, 3.5–5 × 0.1–0.2 mm, subulate, glabrous. Leaves distichous, alternate, terminal pair of leaves subopposite, subsequent leaves subequal, short petiolate or sessile, petioles 0.8–2.0 mm, glabrous; laminae 80–90 × 20–28 mm, length: width ratio 1:3.2–4.0, asymmetrically narrow obovate to oblong, chartaceous, 3-plinerved, the lateral nerves 2–6, borne 45–60° to the midrib; upper surface drying yellow-green, glabrous, cystoliths randomly scattered, conspicuous or inconspicuous, bacilliform, 0.2– 0.3(–0.4) mm; lower surface drying yellow green, glabrous, cystoliths randomly scattered, randomly scattered, bacilliform, 0.2–0.3(–0.4) mm; base asymmetrical, obliquely cuneate; margin serrate, the teeth spaced 6–8 mm apart; apex long acuminate or cuspidate, entire. Staminate and pistillate inflorescences borne on separate stems? Pistillate inflorescences not seen. Staminate inflorescences solitary, axillary, 5–10 mm in diameter, bearing 28–35 flowers in a pedunculate receptacle; peduncle 18–35 x 0.8–1.0 mm, glabrous, apparently ebracteate; receptacle 3–5 mm × 2–2.5 mm, oblong, undivided or deeply two-lobed, glabrous, green above, green below, subtended by marginal bracts, the bracts unequal, major bracts 2, borne opposite each other, at two sides of the receptacle, ca 4 × 1.5 mm, linear–triangular, subapically 1-corniculate; minor bracts 6–13, digitate, 1.8–2.2 × 2.4–4 mm, narrowly triangular, linear–triangular or triangular. Staminate flowers ca. 2.5 × 2 mm immediately prior to anthesis ellipsoid, pedicellate, bracteolate; pedicel 1.5–2.2 mm, glabrous; bracteoles 2 per flower, unequal, major bracteole linear, ca. 3 × 1.2 mm, minor bracteole linear, ca. 1.0 × 0.8 mm, membranous, glabrous; tepals 4, ca. 2 × 1.5 mm, subapical appendage ca. 1 mm, corniculate, green, glabrous.

Distribution and ecology: growing in the shade of small trees and shrub on limestone Karst hillsides, rare, ca. 90–100 individuals.

Etymology: Elatostema laevicaule is named for its glabrous stems.

Vernacular name: Chinese (Mandarin): guangjing louticao, meaning ‘glabrous stems’.

Discussion: Most closely resembles Elatostema filipes Wang (1980: 49) from which it can be distinguished by the length and shape of the stipules, the number and shape of the staminate receptacle bracts and the shape of the staminate bracteoles as summarized in the Table 1 below:

Conservation status:—A Global Conservation Assessment is presented here based on IUCN methodology (2001, version 3.1). Elatostema laevicaule is known from a single locality (criteria D2) where the population numbers ca 100 mature individuals growing in a single cluster (criteria D1 = <250). Plausible future threats that could drive this taxon to Critically Endangered or Extinct in a very short time are mining or conversion to agriculture of the limestone hills on which this species grows. Using the IUCN methodology the Global Conservation Assessment for E. laevicaule would be Endangered (EN) according to criteria D. Much of the plant diversity of limestone karsts of Guangxi has been poorly documented, however, and it may be that future exploration in the area will encounter further populations. For this reason we downgrade the assessment to Vulnerable (VU) based on criteria D1 and D2.

Figures

FIGURE 1, A–C. Elatostema laevicaule W.T. Wang Y.G. Wei & A.K. Monro: A, Habit with leaves, stipules and staminate inflorescences visible; B, Staminate inflorescence with marginal receptacle bracts and flowers; C, Major and minor bracteoles. D, Stipule. (A–B Illustration by Ying-Bao Sun from the holotype; C Illustration by Wen-Hong Lin from isotype; D Illustration by Fang Wen from isotype).

FIGURE 2, A–C. Elatostema laevicaule W.T. Wang Y.G. Wei & A.K. Monro: A, Stem with leaves and staminate inflorescences visible; B, Staminate inflorescence with staminate flowers; C, habit. (A–C by Yi-Gang Wei from the isotype).