Elatostema androstachyum 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 : 5-7

Elatostema androstachyum W.T. Wang, A.K. Monro & Y.G. Wei , sp. nov. ( Fig. 3 , A–I)

Most similar to Elatostema parvum from which it can be distinguished by the smaller stipules, pedunculate and branched staminate inflorescences and achenes with a greater number of longitudinal ribs.

Type: — CHINA. Guangxi: Mashan county, Jiafang town, limestone Karst hills growing in the shade of shrubs in disturbed vegetation, N 23° 43' 16" E 108° 10' 32", 260 m, 6 April 2009, Y. G. Wei g120, (holotype, PE!; isotype, IBK!). Figure 4A–D .

Perennial herb, terrestrial, monoecious. Not tuber forming but callous forming, callous ca 10 × 12 mm, yellow. Stems 70–125 × 0.3–0.5mm, decumbent, dark green when fresh, furfuraceous, unbranched, sparsely pubescent, the hairs ca. 0.5 mm, weakly curved to crooked, appressed, internodes 6–10 × 1.2–1.5 mm. Stipules 2 at each node, caducous, ca. 1.3–1.8 mm, subulate, glabrous. Leaves distichous, alternate, terminal pair of leaves subopposite, subsequent leaves subequal, subsessile, petioles ca. 1 mm, glabrous; laminae 28– 72 × 15–36 mm, length: width ratio 1.9–2:1, asymmetrically elliptic or obovate, chartaceous, 3-plinerved, secondary nerves 2–5 pairs, borne 45–60° to the midrib; upper surface drying dark green, glabrous, cystoliths densely distributed, bacilliform, 0.10–0.25 mm; lower surface drying green, the nerves sparsely pubescent, the hairs ca. 0.5 mm, weakly curved, erect, cystoliths absent; base asymmetrical, subauriculate / cuneate; margin serrate, the teeth spaced 5–8 mm apart; apex weakly obtuse, obtuse or mucronate, entire. Staminate inflorescences borne on modified stems, pistillate inflorescences borne on regular stems, modified staminate inflorescence bearing stems 24–30 mm, dark green, unbranched, sparsely pubescent, with caducous stipules and sessile degenerate leaves, the degenerate leaves 4–6 × 3–4 mm, chartaceous, asymmetrically broadly elliptic, 3-plinerved, lacking cystoliths. Staminate inflorescences axillary, solitary or paired, 3–7 mm in diameter, bearing 6–12 flowers in a pedunculate receptacle; peduncle 2–3 mm, furfuraceous, glabrous, ebracteate?; receptacle subglobose, 2.2-2.5 mm in diam., yellow above, yellow below, not divided into lobes, furfuraceous, glabrous, subtended by marginal bracts, the bracts digitate, subequal, 7–20, linear-lanceolate to narrowly ovate, 1–3 × 0.8-1 mm, sparsely pubescent, the hairs ca. 0.1 mm, weakly curved, erect. Staminate flowers 4.5–7.0 x 1.5–2.0 mm at anthesis, white, pedicellate; pedicels 2.5–5.0 mm; bracteoles 2, unequal, membranous, semitransparent, pubescent, major bracteole 1.8–2.5 mm, linear; minor bracteole 1.3–1.6, linear or narrowly triangular; tepals 4, obovate-oblong, ca. 1 mm, fused for basal 1/3 to 1/2, the subapical appendage corniculate, white, pubescent; stamens 4, ca. 1 mm. Pistillate inflorescences axillary, solitary, ca. 3.0 mm in diameter, bearing 14–16 flowers in a subsessile receptacle; peduncle ca. 0.5 x 1 mm, pubescence, the hairs ca. 0.1 mm, weakly curved, erect, ebracteate?; receptacle subglobose, ca. 1.0 mm in diam., not divided into lobes, yellow above, yellow below, subtended by marginal bracts, the bracts equal, ca. 25, 1-1.4 × 0.25 mm, linearlanceolate, sparsely pubescent. Pistillate flowers ca. 0.8 x 0.4 mm, green, pedicellate to subsessile; pedicels 0.2 mm; bracteoles 2, equal, ca. 1 mm, linear, sparsely pubescent, the hairs ca. 0.05 mm; ovary ca. 0.3 mm, ellipsoid; stigma ca. 0.3 mm. Infructescences as pistillate inflorescence; achene ca. 0.65 x 0.3 mm, ovoid, with 5 longitudinal ribs, beige.

Distribution and ecology: — Elatostema androstachyum is known only from the type locality were it grows on limestone rock in the shade of shrubs in disturbed shrub-dominated vegetation on Karst hills. There is evidence of sustained disturbance in the form of grazing animals and deforestation and the locality is at the margin of agricultural land where maize is cultivated. Annual rainfall is ca. 1700 mm per year. Only ca 10 individuals over an area of 25 m 2 were encountered.

Etymology: — Elatostema androstachyum is named for the staminate inflorescences which are borne on modified stems.

Vernacular name: Chinese (Mandarin): xiongsui louticao meaning ‘staminate stem’ since its staminate inflorescences are borne on modified stems.

Discussion: Most similar to Elatostema parvum (Blume) Miq. in Zollinger (1854: 102) from which it can be distinguished by stipule length, the relative length of the staminate inflorescence bearing stem, relative length of the leaves of the staminate inflorescence bearing stem and the diameter of the pistillate inflorescence as summarized in Table 2 below.

Conservation status:—A Global Conservation Assessment is presented here based on IUCN methodology (2001, version 3.1). Elatostema androstachyum is known from a single locality (criteria D2) where the population of this species numbers ca 10 mature individuals (criteria D1 = <250). Plausible future threats that could drive this taxon to Critically Endangered or Extinct in a very short time are the presence of livestock which currently graze this locality and our own observations of active deforestation. Using the IUCN methodology the Global Conservation Assessment for E. androstachyum would be Critically Endangered (EN) according to criteria D. Much of the plant diversity of limestone karsts of Guangxi, however, has been poorly documented and so it may be that future exploration and collecting 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 3, A–H. Elatostema androstachyum W. T. Wang Y. G. Wei & A. Monro: A, habit; B, Staminate stem; C, Staminate inflorescence (seen from the side); D, Staminate bracteoles; E, Staminate flower; F, Pistillate inflorescence (seen from beneath); G, Pistillate flower with pistillate bracteoles; H, Achene; I, Stipule. (A–D, G–H Illustration by Ying-Bao Sun from holotype; E–F Illustration by Wen-Hong Lin from isotype; I Illustration by Fang Wen from isotype).

FIGURE 4, A–D. Elatostema androstachyum W. T. Wang Y. G. Wei & A. Monro: A, Habitat; B, Habit with staminate (centre) and pistillate inflorescences (bottom-right) visible; C, Pistillate inflorescence; D, Staminate inflorescence. (A–D by Yi-Gang Wei from the isotype)