Elatostema nianbense 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 : 17-20

Elatostema nianbense W.T.Wang, Y.G.Wei & A.K.Monro , sp. nov ( Fig. 10 & 11 )

Elatostemo filipis similis sed planta majori monoeca, caulibus pubescentibus, cystolithis numerosis instructis, pedunculis staminalibus majoribus, floribus quintepartitis, receptalaco pistillato majori, differt.

Type:— CHINA. Guangxi: Jingxi County, Tong De Town, Guolao village , Nian Ba gorge, at foot of waterfall in gorge, subtropical evergreen forest, N 23°02'32.1" E 106° 37'28.7", 600 m, 1 March 2009, A. K . Monro , Y. G . Wei & S. N . Lu 6432 (holotype IBK, isotypes BM, MO, PE) .

Perennial herb, terrestrial, monoecious. Not tuber forming. Stems 300–500 × 1.5–5.0 mm, erect to arching, succulent, green, drying finely sulcate or striate, with tufts of hairs at nodes, the hairs 0.75–1.00 mm, straight, weakly appressed, broad based frequently, with a pronounced ring at their base, internodes 15–40 mm. Stipules 1 at each node, persistent, 7–19 mm, lanceolate, glabrous.Leaves distichous, alternate, subsequent leaves unequal, the major leaves subsessile, petioles 2.0–2.5 × 1 mm, pubescent, the hairs 1 mm, weakly curved, erect; the minor leaves sessile, the major laminae 40–140 × 15–50 mm, length:width ratio 1:2.1–3.2, asymmetrically oblong-obovate, subchartaceous, 3-nerved, the secondary nerves 2 or 3 pairs, 30– 45° to the midrib; the minor laminae caducous, ca 5 × ca 3 mm, broadly obovate otherwise as major laminae; upper surface drying bright green, pubescent, the hairs clustered in patches between the secondary nerves, 0.75 mm, curved, appressed, cystoliths densely distributed, bacilliform, <0.2 mm; lower surface drying green, glabrous, the hairs 0.675 –0.750 mm, weakly curved, appressed, cystoliths absent but imprint of upper surface cystoliths visible; base asymmetrical, cordate / decurrent; margins subserrate to base, the teeth spaced 5–10 mm apart; apex subacuminate to attenuate. Staminate inflorescences borne towards the stem apex, pistillate inflorescences borne towards the stem base. Staminate inflorescences solitary, 17–25 mm, bearing 8–10 flowers in a pedunculate receptacle; peduncle 14–37 × 0.50–0.75 mm, pubescent, bracts not seen, caducous?; receptacle 5.5 × 8 mm, subsymmetrical, capitate, not lobed or inconspicuously so, glabous, pale green above, green below, subtended by marginal bracts, the bracts equal, 4–6, 5.5–6.0, triangular, ovate, narrowly ovate, much reduced or absent to one side of the receptacle, pale green to very pale green, transluscent. Staminate flowers 3.0–3.5 × 2 mm immediately prior to anthesis, cream to fuchsia pink, pedicellate, bracteolate; pedicel 3.5–4.0 mm, glabrous; bracteoles 2, equal, 3.5–4.0 mm, triangular or oblanceolate-linear; tepals 4 or 5, the subapical appendage 0.75 mm, corniculate, green. Pistillate inflorescence solitary, 3.5–4.5 mm, bearing 50–90 flowers in a pedunculate receptacle; peduncle 0.50–0.75 × 0.375 –0.500 mm, glabrous bracteate; bracts 0.750 – 0.375 mm, subulate; receptacle 3.0–3.5 × 2.5–2.8 mm, angulate to ovate, 2-lobed, glabrous, bright green above, green below, subtended by marginal bracts, the bracts unequal, major bracts 2, 5 mm, assymetrically deltate, minor bracts 8, 3.5 mm, forked, subminor bracts 16, 1.5–2.0 mm, subulate, green. Pistillate flowers 0.5 × <0.2 mm at anthesis, cream, subsessile; bracteoles 2, equal, 0.500 – 0.675 mm, linear-oblanceolate, ciliate. Infructescences as pistillate inflorescences; achene 0.60 × 0.25 mm, narrowly ellipsoid or subfusiform with narrow longitudinal ridges, pale brown to cream.

Distribution:—Known from a single collection from Jingxi County, Guangxi. Elatostema nianbense is found growing in a large dense clump at the base of a waterfall in an isolated gorge.

Etymology:—after the collection locality: Nian Ba gorge.

Discussion:— Elatostema nianbense is most similar to E. filipes Wang (1980) , from which it can be distinguished based on its sexual system, stems, leaves, staminate inflorescences and flowers, and pistillate inflorescence 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 nianbense was found at a single locality (IUCN criteria D2) where a single population of ca 500–1000 individuals was observed (IUCN criteria D1). Whilst the locality is isolated (a gorge) and the vegetation seems relatively undisturbed by human activities, it is close to a road and the vegetation above the southwestern face of the gorge from where the waterfall originates has been heavily deforested. Using the IUCN methodology our Global Conservation Assessment for E. nianbense is Vulnerable (VU) based on criteria D1 and D2: the restricted number of locations and small population size combined with a plausible future threat could drive this taxon to Critically Endangered or Extinct in a very short time. Future threats could include agriculture, mining and local tourism.

Figures

FIGURE 10. Elatostema nianbense. A. Habit with leaves, stipules, staminate and pistillate inflorescences visible. B. Staminate inflorescence with marginal receptacle bracts, staminate flowers and subapical corniculate tepal appendages visible. C. Staminate bracteoles. D. Pistillate inflorescence viewed from below with marginal bracts visible. E. Pistillate flower and bracteole. F. Achene. Monro, Wei & Lu 6432, IBK (Illustration by Sun Ying-Bao).

FIGURE 11. Elatostema nianbense. A. Habitat, base of waterfall in the Nian Ba gorge surrounded by subtropical evergreen forest. B. Staminate inflorescence with marginal receptacle bracts, staminate flowers and anthers visible. C. Pistillate inflorescence with marginal bracts and flower clusters visible. Monro, Wei & Lu 6432 (Photo A.K. Monro).