Elatostema retrorstrigulosum 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 : 20-23

Elatostema retrorstrigulosum W.T.Wang, Y.G.Wei & A.K.Monro , sp. nov. ( Fig. 12 & 13 )

Elatostemo balanae similis sed caulibus pubescentibus pilis retrorsis majoribus obtectis, stipulis minoribus, bracteis inferioribus receptaculi pistillati majoribus.

Type:— CHINA. Guangxi: Napo County, in small grotto in stalagmite in cave, N 24°24'47.8" E 107°01'16.4", 550 m, 9 May 2010, A. K . Monro & Y. G . Wei 6677 A (holotype IBK, isotypes BM, MO, PE) .

Perennial herb, terrestrial, epipetric, dioecious?. Not tuber forming. Stems 150–360 × 1–2 mm, erect or decumbent, smooth, subsucculent, dark green, densely pubescent, the hairs 1.000 –1.250 mm, curved and erect, appressed, mainly retrose but not exclusively so, internodes 8–15 mm. Stipules 2 at each node, persistent, 4.0– 6.5 mm, lanceolate, sparsely pubescent. Leaves distichous, alternate, subsequent leaves subequal, the major leaves short petiolate to subsessile, petioles 0.5–3.0 × 0.75 mm, pubescent, the hairs 0.75 mm, straight, appressed ascendent; laminae 37–115 × 23–60 mm, length:width ratio 1:2.2–3.0, asymmetrically elliptic, elliptic/obovate, cordate/obtuse. cordate / cuneate, chartaceous, 3-nerved, the secondary nerves 2 or 3 pairs, 45°–60° to the midrib; upper surface drying yellow-green, sparsely pubescent, the hairs 1.0 mm, straight or weakly curved, appressed, ascendent, cystoliths densely distributed, fusiform, 0.250 –0.375 mm; lower surface drying grey-green, primary and secondary nerves pubescent, the hairs 0.250 – 0.375 mm, straight, erect, cystoliths absent but imprint of upper surface cystoliths visible; base asymmetrical, decurrent/cuneate, decurrent/minutely cordate; margins serrate-dentate, basal ≤ entire, the teeth spaced 10 mm apart; apex acuminate. Placement of staminate and pistillate inflorescences unknown. Staminate inflorescences not seen. Pistillate inflorescence solitary, 1.5–3.0 mm, bearing 100 flowers in a subsessile to pedunculate receptacle; peduncle 0.5–1.0 × 0.375 mm, sparsely pubescent, ebracteate?; bracts not seen; receptacle 3 × 2.5–5.5 mm, broadly rectagular, rhombic, 2-lobed, glabrous, green above, green below, subtended by marginal bracts, the bracts unequal, green, major bracts 3, 2 mm, corniculate to trapeziform and corniculate, minor bracts 4, 1.5 mm, broad deltate and 4-corniculate. Pistillate flowers 0.500 –0.675 × 0.25 mm at anthesis, very pale green to cream, subsessile to sessile; bracteoles 2, equal, 0.6–1.2 mm, linear or oblanceolate-linear. Infructescences not seen.

Distribution:—Known only from the type locality in Napo County Guangxi, Southwest China. Elatostema retrostrigulosum is known only from caves formed in limestone karst at elevations of ca 600 m. This species grows both close to the entrance and in a small grotto within the main cavern in ca 1% daylight (photosynthetically active radiation).

Etymology:— Elatostema retrorstrigulosum is named after the retrorse hairs growing densely on the stem.

Additional specimen examined (paratype):— CHINA. Guangxi: Napo County, in small grotto in stalagmite in cave, N 24°24'47.8" E 107°01'16.4", 550 m, 21 March 2009, Y. G . Wei g057 ( BM, IBK, MO, PE) .

Discussion:— Elatostema retrorstrigulosum is most similar to Elatostema balansae Gagnepain (1929) from which it can be distinguished based on stem, leaf and staminate inflorescence and flower morphology, 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 retrorstrigulosum is known from a single cave locality (IUCN criteria D2, ≤5). The population consists of less than 10 mature individuals (IUCN criteria D, <50). Using the IUCN methodology our Global Conservation Assessment for E. retrorstrigulosum is Endangered (E) based on criteria D1 and D2: population size and number of locations combined with a plausible future threat that could drive this taxon to Critically Endangered or Extinct in a very short time. The cave locality has a road running through it and is a popular local tourist stop. Future threats could include the development of tourism in this area and the use of caves to store livestock.

Figures

FIGURE 12. Elatostema retrorstrigulosum. A. Habit with stipules and pistillate inflorescences visible. B. Pistillate inflorescence viewed from below with receptacle bracts visible. C. Pistillate flower with bracteole. Monro & Wei 6677A, IBK (Illustration by Sun Ying-Bao).

FIGURE 13. Elatostema retrorstrigulosum. A. Cave habitat locality for Monro & Wei 6677A. B. Habit, Elatostema retrorstrigulosum (Y.G.Wei g057). C. Pistillate inflorescence viewed from below with receptacle bracts visible (Monro & Wei 6677A). D Pistillate inflorescence viewed from above with bracteoles and achenes visible (Monro & Wei 6677A), (Photo A.K. Monro (Monro & Wei 6677A), (Y.G. Wei g057).