Three New Species of Elatostema (Urticaceae) from Guangxi

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http://dx.doi.org/10.11646/phytotaxa.147.1.1

Additions to the Flora of China: three new species of Elatostema (Urticaceae) from Guangxi

YI-GANG WEI1, A.K. MONRO2,4* & WEN-TSAI WANG3 1Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and the Chinese Academy of Sciences, CN-541006 Guilin, China 2Herbarium, Royal Botanic Gardens, Kew, TW9 3AB, United Kingdom. E-mail: [email protected] 3State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, CN-100093 Beijing, China 4Life Sciences Department, The Natural History Museum, London SW7 5BD, United Kingdom. * Author for correspondence

Abstract

Three new species are described and illustrated and their conservation status assessed: Elatostema laevicaule W.T. Wang, A.K. Monro & Y.G. Wei, E. androstachyum W.T. Wang, A.K. Monro & Y.G. Wei and E. heterocladum W.T. Wang, A.K. Monro & Y.G. Wei. All are rare endemic species from Guangxi Province, China, and are only known only from their type localities. E. laevicaule is most similar to E. filipes and is assessed as Vulnerable (VU), E. androstachyum is most similar to E. parvum and is assessed as Vulnerable (VU); E. heterocladum is most similar to both E. androstachyum and E. luxiense and is assessed as Vulnerable (VU).

Introduction

Elatostema J.R. Forster & G. Forster (1775: 53; Urticaceae) consists of understory herbs and subshrubs that occur in the deep shade of forests, stream sides, gorges and caves. Elatostema occurs throughout tropical and subtropical Africa, Asia, Australia, and Oceania but is notably absent from the Neotropics. In Southeast Asia the genus is most diverse on limestone karst (Yahara 1984, Lahav–Ginott & Cronk 1993, Wang & Chen 1995, Qi et al. 2003). Elatostema appears to be of little economic use although several species are used in combination with other plants in traditional folk medicine in Southeast Asia and the Pacific (Bourdy & Walter 1992, Nandwani et al. 2008, He et al. 1991). Elatostema forms part of a complex of genera which includes Elatostematoides Robinson (1911: 497), Pellionia Gaudichaud in Freycinet (1830: 494) and Procris Commerson ex Jussieu in Jussieu (1789: 403) whose generic limits are difficult to define. Of these, Elatostema is the oldest name (Forster 1775). Elatostematoides has not been widely recognized or used since its description by Robinson (1911) and is widely treated as Elatostema (Friis 1989). There is however little consensus as to the delimitation of Elatostema, Pellionia and Procris. Disagreement has centred on the use and interpretation of two main suites of characters, inflorescence branching morphology and staminate flower perianth morphology. The recent incorporation of DNA sequence data from the plastid genome (Hadiah et al. 2003, Wu et al. 2013.) has done little to resolve generic delimitation. To date, 1121 species names of the Elatostema complex of genera (Elatostema, Elatostematoides, Pellionia and Procris) have been published (IPNI 2013) and current published species estimates range from 250 (Chew 1989) to 400 species (Yahara 1984). Assuming levels of synonymy of only 10% as for Pilea (Monro 2004), a genus with similar habit and habitat, the species number could be ca 1000. Within China 210 species are reported and of these 64 have been described subsequent to the Flora of China treatment of 2003 (Duan & Lin 2010, Lin & Duan 2008, Lin et al. 2011, Wang 2003, 2006, 2010a,

Accepted by Libing Zhang: 27 Sept. 2013; published: 20 Nov. 2013 1 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited.

2010b, 2011, 2012, Wang & Wei 2007, 2008, Wei & Wang 2009a, 2009b, 2011a, 2011b,l Wei. 2011, et a 2012, Wu et al. 2011a, 2011b, 2012, Yang et al. 2011). As part of botanical surveys of Guangxi conducted by the authors in recent years three hitherto undescribed species have been collected. These are described and illustrated here. These species are described from single collections. Describing species based on a single or only two collections is problematic and ill- advised as there is no estimate of variation within the species and so the risk of recognising too many species is increased. This is compounded in Floras such as China’s where there is a tradition of describing species from single collections as the most closely related species may also only be known from a single collection. Despite the above we have decided to describe the species in this manuscript as we feel confident based on morphological species concepts that this material represents distinct species. In addition we feel that given China’s fast changing landscape and the fragility of many of the localities that to describe the species now affords the best hope for their documentation and subsequent conservation.

Materials and methods

Herbarium specimens were compared with the collections at K, IBK, PE and BM. A morphological species concept is used that was developed as part of previous taxonomic research (Wei et al. 2011). Material was examined under a Changfang XTL-240 binocular microscope and Planapo lens at ×14 to ×90 magnification and ca 130 observations made for each taxon. Conservation Assessments were undertaken using IUCN criteria (IUCN 2001). Species localities were plotted on Google Earth and the nature of the vegetation cover, urbanization and road proximity surrounding sites, combined with observations in the field were used as indicators of plausible future threats. Given the restricted distributions and populations of these species Criteria D was applied in all cases. Although for many assessments criteria D1, the number of mature individuals observed would have sufficed we decided that given the naturally restricted size of a cave or gorge dwelling population that criteria D1 should only be applied in combination with criteria D2, which includes the qualification of plausible threat. Criteria D2, ‘Restricted area of occupancy or number of locations with a plausible future threat that could drive the taxon to Critically Endangered or Extinct in a very short time’ (IUCN 2001).

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,

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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).

THREE NEW SPECIES OF ELATOSTEMA FROM GUANGXI Phytotaxa 147 (1) © 2013 Magnolia Press • 3 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. 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.

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).

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:

TABLE 1. Diagnostic comparison of Elatostema laevicaule and E. filipes.

Characters E. laevicaule E. filipes

Stipules subulate, 3.5–5.0 mm lanceolate, 7–9 mm Staminate bracts Minor bracts 6–13, narrowly triangular, not corniculate Minor bracts 3–6, broadly ovate, corniculate bracteoles not corniculate major bracteoles corniculate

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

4 • Phytotaxa 147 (1) © 2013 Magnolia Press WEI ET AL. TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. 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.

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, linear- lanceolate, 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 m2 were encountered.

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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).

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.

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TABLE 2. Diagnostic comparison of Elatostema androstachyum and E. parvum.

Characters E. androstachyum E. parvum Stipule length and shape ca. 1.8 mm, subulate 4–7 mm, lanceolate or linear Relative length of staminate inflorescence bearing stem to sterile or < 1/4 > ½ or equal pistillate inflorescence bearing stems Relative length of leaves of staminate inflorescence bearing stems to 1: 6–10 subequal or equal leaves of sterile or pistillate inflorescence bearing stems Pistillate inflorescence diameter ca. 3.0 mm 4–6 mm

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)

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.

Elatostema heterocladum W.T. Wang, A.K. Monro & Y.G. Wei, sp. nov. (Fig. 5, A–G) Most similar to E. androstachyum from which it can be distinguished by the stems maroon without scales; the inflorescence subtended by broad-ovate, staminate bracts two classes, major bracts 2, apex corniculate, minor bracts 4–6, with a truncate, erose apex and pistillate bracts ca. 6, with a cucullate apex, glabrous. Also most similar to E. luxiense from which it can be distinguished by the stems lacking small irregularly shaped brown scales, the

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possession of dwarf staminate stems which bear leaves that are strongly reduced in size and which lack cystoliths; the inflorescence subtended by broad-ovate bracts and staminate flowers subtended by linear bracteoles. Type: —CHINA. Guangxi: Longlin county Dahongbao nature reserve, N 24°57′ 44" E105°09′35″, 1150 m, 27 March 2009, Y.G. Wei g086, (holotype PE!, isotype IBK!, BM!). Figure 6A–C.

FIGURE 5, A–F. Elatostema heterocladum W.T. Wang, Y.G. Wei & A. Monro: A, Staminate stem and pistillate stem; B, Staminate inflorescence; C, Staminate bracteoles; D, Young pistillate inflorescence; E, Pistillate bract; F, Two pistillate bracteoles; G, Staminate bract. (A–F Illustration by Ying-Bao Sun from holotype; G Illustration by Fang Wen from isotype).

Perennial herb, terrestrial, dioecious. Not tuber forming. Stems ca. 240–300 x 2.0–2.5 mm, decumbent, maroon when fresh, branched, glabrous, internodes 5–9 mm. Stipules 2 at each node, caducous, 1.5–1.8 ×

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0.2–1 mm, narrowly linear, glabrous. Leaves distichous, alternate, the terminal pair of leaves subopposite, subsequent leaves subequal, petioles 0.5–1.5 mm, glabrous; laminae 50–140 × 20–44 mm, length: width ratio 1.5–3.18:1, asymmetrical, elliptic or oblong, chartaceous, 3-plinerved, the secondary nerves 2- 4, 60–90° to the midrib; upper surface drying dark green, glabrous, cystoliths densely or sparsely scattered, inconspicuous, bacilliform, 0.10–0.25 mm; lower surface drying brown-yellow, glabrous, cystoliths absent; base asymmetrical, cordiform/cuneate or obtuse/cuneate; margin serrate, the teeth spaced 5–9 mm apart; apex acuminate to caudate. Staminate and pistillate inflorescences borne on separate stems, modified staminate inflorescence bearing stems decumbent, simple or branched, with degenerate sessile or short petiolate leaves, 5–27 × 1.5–5 mm, oblong–linear, 1-nerved, cystoliths absent. Staminate inflorescences solitary, borne on modified stems, axillary, bearing 15–25 flowers in a pedunculate receptacle; peduncle 9–25 mm, glabrous, ebracteate?; receptacle 8–11 x 3–6 mm, discoid, not lobed, brown-yellow above, brown-yellow below, glabrous, subtended by marginal bracts, the bracts unequal, major bracts 2, borne opposite each other, at two sides of the receptacle, 3.8–5.0 × 2.4–4 mm, not erect, broadly ovate with a cucullate apex, the point of the apex corniculate, minor bracts 4-6, erect, 1.8–2.2 × 2.4-4 mm, broadly ovate with a truncate, erose apex. Staminate flowers ca. 5.0 x 3.0 mm at anthesis, white, pedicellate; pedicel ca. 2 mm, glabrous; bracteoles 2, unequal, major bracteole ca. 4.2 mm, linear, glabrous, minor bracteole ca. 2.0 mm, linear, glabrous; tepals 4, 3 × 1 mm, obovate-oblong, fused and connate towards the base, pale green, the subapical appendage 0.5-0.6 mm, corniculate, glabrous, stamens 4. Pistillate inflorescences axillary, solitary, pedunculate; peduncle ca. 0.6 mm, glabrous, ebracteate?; receptacle 2 mm in diameter, oblong, brown above, brown below, subtended by marginal bracts, the bracts equal, ca. 6, erect, broadly ovate with a cucullate apex terminating in a corniculate appendage, glabrous. Pistillate flowers immature; bracteoles 2 per flower, unequal, major bracteole 0.4 mm, broadly ovate, apically corniculate, glabrous or sparsely pubescent, where pubescent the hairs ca. 0.1 mm, minor bracteole 0.3 mm, broadly ovate. Infructescences not seen.

FIGURE 6, A–C. Elatostema heterocladum W.T. Wang, Y.G. Wei & A. Monro: A, Habit and staminate inflorescences; B, Young pistillate inflorescence; C, Staminate inflorescences showing bracts, flowers and anthers. (A–C by Yi-Gang Wei from the isotype).

Distribution and ecology: Elatostema heterocladum is known only from the type locality growing on limestone hillsides in the shade of small trees and shrubs in disturbed vegetation. Mean annual rainfall at the type locality is ca 1100 mm. Ca. 90 individuals were seen growing in a single cluster.

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Etymology: Elatostema heterocladum is named after staminate inflorescences borne on specialised stems which differ from those on which pistillate inflorescences are borne. Vernacular name: Chinese (Mandarin): yijing louticao, meaning ‘different stem’, a reference to there being a modified staminate stem contrasting to a normally developed pistillate stem. Discussion: Elatostema heterocladum may be easily distinguished from many other species in the genus, including those cited as most similar below by the delicate staminate inflorescence-bearing stems that bear greatly reduced leaves together with the discoid staminate receptacle. E. heterocladum is most similar to E. androstachyum and E. luxiense Wang (1982: 18). It can be distinguished from E. androstachyum by stem, solitary staminate inflorescence, staminate bract and pistillate bract morphology as summarized in Table 3. It can be distinguished from E. luxiense W.T. Wang by leaf morphology and staminate inflorescence morphology as summarized in Table 4.

TABLE 3. Diagnostic comparison of Elatostema heterocladum and E. androstachyum.

Characters E. heterocladum E. androstachyum Stem colour and indumentum Maroon, without scales dark green, with small irregular brown scales Staminate receptacle bracts Two classes of bract present, major bracts 2, A single class of bract present, bracts 7–20, broadly ovate, the apex corniculate; linear-lanceolate to narrowly ovate, the apex not corniculate; minor bracts 4-6, broadly ovate with a truncate, erose apex Pistillate bracts ca. 6, broadly ovate with a cucullate apex, ca. 25, linear-lanceolate, sparsely pubescent glabrous

TABLE 4. Diagnostic comparison of Elatostema heterocladum and E. luxiense.

Characters E. heterocladum E. luxiense Relative length of leaves of staminate-inflorescence bearing stems to 1/10 to 1/2 equal leaves of sterile or pistillate inflorescence bearing stems Staminate bracts broadly ovate linear or oblong Staminate bracteoles 2.0–4.2 mm long, linear ca. 1 mm long,lanceolate

Conservation status:—A Global Conservation Assessment is presented here based on IUCN methodology (2001, version 3.1). Elatostema heterocladum is known from a single locality (criteria D2) where the population numbers ca 90 mature individuals (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 grow. Using the IUCN methodology the Global Conservation Assessment for E. heterocladum would be Critically Endangered (EN) according to criteria D. Much of the plant diversity of limestone karsts of Guangxi 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.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 3116039), the Innovation Fund of the Botany Department of The Natural History Museum, a Travel Grant from the Royal Society and the Science Research Foundation of Guangxi Institute of Botany (No. 10004). We would also like

10 • Phytotaxa 147 (1) © 2013 Magnolia Press WEI ET AL. TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. to thank our driver Wei-Hua Li, Sun Ying-Bao, Lin Wen-Hong and Wen Fang for the illustrations and Fa-Nan Wei (IBK) for help with earlier darfts of this manuscript.

References

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THREE NEW SPECIES OF ELATOSTEMA FROM GUANGXI Phytotaxa 147 (1) © 2013 Magnolia Press • 11 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited.

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