Research Article |
Corresponding author: Zhi-Xiang Zhang ( zxzhang@bjfu.edu.cn ) Academic editor: Clifford Morden
© 2019 Long-Fei Fu, Alexandre K. Monro, Fang Wen, Zi-Bing Xin, Yi-Gang Wei, Zhi-Xiang Zhang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Fu L-F, Monro AK, Wen F, Xin Z-B, Wei Y-G, Zhang Z-X (2019) The rediscovery and delimitation of Elatostema setulosum W.T.Wang (Urticaceae). PhytoKeys 126: 79-88. https://doi.org/10.3897/phytokeys.126.35707
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Of the 280 species of Elatostema documented in China, 189 are known only from a single collection. Elatostema setulosum is one such species, having been known only from the type collection for nearly half a century, until recent field investigations in Guangxi. Due to its morphological similarity to E. huanjiangense and E. tetracephalum, we undertook a critical review of all three species using morphological and molecular evidence. Our results suggest that all three names refer to the same species, which based on priority should be known as Elatostema setulosum. We recognize E. huanjiangense and E. tetracephalum as synonyms. A distribution map of E. setulosum and the extinction risk according to the IUCN criteria is provided. After recircumscription, the taxon must be considered as Least Concern (LC).
Taxonomy, synonymy, Elatostema huanjiangense, Elatostema tetracephalum, China, Guangxi, Guizhou, Rosales, karst landscapes
Elatostema J.R.Forst. & G.Forst. (Urticaceae) is one of two species-rich genera in the Urticaceae, comprising several hundred species of herbs and subshrubs that grow under shade in forests, gorges, stream-sides and caves (
The first revision of Chinese Elatostema was undertaken by
Karst landscapes are characterized by exposed rocks with shallow soils deficient in N and P, but with excessive Ca and Mg that are subject to seasonal droughts and an absence of surface water (
Collecting in karst, however, is difficult as there are relatively few roads and the terrain is steeply dissected, the very sharp eroded surfaces making it difficult and dangerous to traverse. As a consequence, there are relatively few collections from such areas and undescribed species are frequently known by only one or two collections. Based on
Elatostema setulosum W.T.Wang was described from a single specimen (holotype) in 1982. This specimen was first identified as Elatostema sessile var. polycephalum Wedd. in 1964, but later raised to specific rank by Wang in 1982. No additional material was collected until June 2018, at which time a population was discovered close to the type locality. In identifying this recently collected material, we observed that it was morphologically very similar to several species, E. pergameneum W.T.Wang, E. huanjiangense W.T.Wang & Y.G.Wei and E. tetracephalum W.T.Wang, Y.G.Wei & F.Wen, the latter considered to be a synonym of E. huanjiangense by
In order to clarify the relationship among E. huanjiangense, E. setulosum and E. tetracephalum, we undertook a critical examination and comparison of all collections of these related species based on morphological and molecular evidence.
Fieldtrips in Guangxi and Guizhou were undertaken between 2007 and 2018 to collect specimens of Elatostema huanjiangense, E. pergameneum, E. setulosum and E. tetracephalum which were deposited at BM, IBK, K and PE. For all collections, samples of leaf material were dried in the field using silica gel for use in DNA extraction (
Two universal barcodes: the nuclear ribosomal internal transcribed spacer (ITS) region and the trnH-psbA intergenic spacer were used to establish hypotheses of evolutionary relationships due to their ability to detect variation at the species level (
To elucidate phylogenetic relationships between the ingroup taxa, Elatostema huanjiangense, E. pergameneum, E. setulosum and E. tetracephalum, we analyzed three accessions of E. huanjiangense, and one of E. pergameneum, E. setulosum and E. tetracephalum. As outgroups, we selected E. grijsii (Hance) Y.H.Tseng & A.K.Monro and E. scabrum (Benth.) Hallier f. based on the most recent published phylogeny for Elatostema, Elatostematoides and Procris (
Species name, voucher specimen and accession numbers of trnH-psbA and ITS used in this study (*denoted newly generated sequences).
Speices name | Voucher specimen | trnH-psbA | ITS |
---|---|---|---|
Elatostema grijsii (Hance) Y.H.Tseng & A.K.Monro | Y.H. Tseng 1167 | KC420504 | KC420491 |
Elatostema huanjiangense W.T.Wang & Y.G.Wei | Y.G. Wei g124 | KP858730 | KP858875 |
Elatostema huanjiangense W.T.Wang & Y.G.Wei | A.K. Monro & L.F. Fu 7705 | MK656519* | MK651815* |
Elatostema huanjiangense W.T.Wang & Y.G.Wei | A.K. Monro & L.F. Fu 7719 | MK656518* | MK651816* |
Elatostema pergameneum W.T.Wang | Y.G.Wei 07298 | MK656516* | MK651817* |
Elatostema scabrum (Benth.) Hallier f. | Y.H. Tseng 1219 | KC420503 | KC420492 |
Elatostema setulosum W.T.Wang | L.F. Fu et al. FLF180606-01 | MK656515* | MK651813* |
Elatostema tetracephalum W.T.Wang, Y.G.Wei & F.Wen | A.K. Monro & L.F. Fu 7696 | MK656517* | MK651814* |
Sequence data were edited and assembled using the software Lasergene Navigator (DNAStar, Madison, Wisconsin, USA). Edited sequences were then aligned with the MEGA 5.1 (
Distribution map of Elatostema huanjiangense, E. setulosum and E. tetracephalum was made using the software ArcGIS 10.2 (ESRI, Inc.).
A morphological species concept was employed to compare the taxa based on
The combined matrix had a length of 1036 characters, 715 for ITS and 321 for trnH-psbA. Of the 208 (20.1%) variable characters, 117 (11.3%) were parsimoniously informative, including the indels. The maximum parsimony analysis on the combined matrix resulted in three equally parsimonious trees of 241 steps long, a consistency index (CI) of 0.959, retention index (RI) of 0.938 and homoplasy index (HI) of 0.041. MP and BI analyses have same topology (Fig.
Maximum parsimony phylogenetic tree based on the combined trnH-psbA and ITS data, showing relationships of Elatostema huanjiangense, E. pergameneum, E. setulosum and E. tetracephalum. Numbers on the branches indicate bootstrap values (≥60%) of the maximum parsimony analysis and the posterior probability (≥0.8) of Bayesian inference analysis.
CHINA. Guangxi: Tianyang County, Anning Gongshe, Anon. 262 (holotype: IBK![IBK00200113]). = Elatostema huanjiangense W.T.Wang & Y.G.Wei, 2007: 816. Syn. nov. Type: China. Guangxi: Huanjiang County, Mulun, Hongdong, 19 April 2006, Y.G. Wei 06128 (holotype: PE![02050267]). = Elatostema tetracephalum W.T.Wang, Y.G.Wei & F.Wen, 2012: 1100. Syn. nov. Type: China. Guizhou: Huangping County, in forest of earth mount, 20 March 2010, Y.G. Wei & F. Wen 1067 (holotype: PE!, isotype: IBK!).
Perennial herb, terrestrial, dioecious. Stem 50–250 × 2–3 mm, ascending or erect, simple or branched, glabrous. Stipule 2, persistent, 2–2.2 × 0.2 mm, lanceolate-linear, glabrous. Leaves distichous, alternate, sessile or short petiole; laminae 30–150 × 14–60 mm, length:width ratio 2.1–2.5:1, obliquely elliptic, papery; triplinerve or rarely semitriplinerve; abaxial surface glabrous, adaxial surface sparsely setulose; cystoliths densely scattered, bacilliform; base asymmetrical, broader-half rounded or auriculate, narrower-half cuneate; margin crenate; apex shortly acuminate or acuminate. Staminate and pistillate inflorescences not borne on the same stems. Staminate inflorescences paired, axillary, cymiferous, bearing ca. 30 flowers, ca. 10 mm in diam., peduncle 1.6 × 0.4 mm, subglabrous; bracts membranous, linear-lanceolate or lanceolate-linear, 1.2–2.5 × 0.3–1 mm, sparsely ciliate; staminate flower bud ovoid, flowers ca. 1.6 × 1 mm, glabrous, tepals 5, subapical appendage ca. 1 mm, corniculate. Pistillate inflorescences paired, axillary, capitate, bearing ca. 20 flowers, inflorescences with three types: (1) simple capitulum, 1.5 mm in diam., receptacle inconspicuous, bracts ca. 10; (2) composite capitulum, comprised by four 2-branched simple capitulum; (3) simple capitulum, receptacle discoid-oblong, 2–3 × 0.8–2 mm, weakly divided into two lobes, glabrous, subtended by marginal bracts; bracts numerous, triangular, ca. 0.5 × 0.2–0.3 mm, glabrous; bracteoles 2 per flower, subequal, 0.5–1 mm, linear, semitransparent; Pistillate flowers: ovary ovoid, ca. 0.6 mm; achene 6.122–7.99 × 3.891–5.119 mm, length:width ratio 1.56–1.57:1, broadly ellipsoid, with 4 longitudinal ribs and tuberculate, two opposite longitudinal ribs winged.
CHINA. Guangxi: Huanjiang County, Mulun nature reserve, Hongdong, 8 April 2009, Y.G. Wei g124 (IBK!, PE!); Huanjiang County, Mulun nature reserve, Leyi Village, Donglai, 3 May 2011, Y.S. Huang, Y.B. Liao & R.C. Peng y0216 (IBK!); Huanjiang County, Mulun nature reserve, Leyi Village, Donglai, 18 April 2012, W.B. Xu, R.C. Peng & R.C. Hu ML1037 (IBK!); Huanjiang County, Mulun nature reserve, Hongdong, 16 April 2012, L.F. Fu FL004 (IBK!, PE!); Huanjiang County, Chuanshan Town, on the way from Hongdong to Zhonglun, 9 May 2006, Man-Fu Hou 117 (PE!); Tianyang County, Babie Village, Anning Village, 6 June 2018, L.F. Fu, Y.C. Liu & W.J. Xu FLF180606-01 (IBK!); Guizhou: Huangping County, Feiyun gorge, 17 May 2012, Y.H. Tseng & L.F. Fu Zn1217 (IBK!), 8 Nov. 2015, A.K. Monro & L.F. Fu 7696 (IBK!, K!); Shibing County, Yun Tai Mountain, 10 Nov. 2015, A.K. Monro & L.F. Fu 7705 (IBK!, K!); Zhen Yuan County, Tiexi Tourist Park, 10 Nov. 2015, A.K. Monro & L.F. Fu 7719 (IBK!, K!).
An Extinction Threat Assessment was undertaken using the IUCN methodology (2012). Elatostema setulosum is known from five localities in Guangxi (one population) and Guizhou (four populations), China. We estimate that the population of mature individuals is greater than 1000. The given surface area of a polygon including the known localities for this species is greater than 27,000 km2 (Fig.
We would like to thank the staff at BM, IBK, K and PE who provided help for checking specimens. We are also grateful to Mr. Yu-Chun Liu from National Taiwan University and Ms. Wen-Jing Xu from Anhui University for participating in fieldwork. We extend our appreciation to Dr. Shen-Jian Xu from Beijing Forestry University (BFU) for dealing with images and Dr. Hong-Fei Zhuang from BFU for preparing the distribution map. This work was supported by the National Natural Science Foundation of China (grant number 31570307), Guangxi Natural Science Foundation Program (grant number: 2017GXNSFBA198014) and the STS Program of the Chinese Academy of Sciences (grant number: KFJ-3W-No1).