Research Article |
Corresponding author: Liang Zhang ( zhangliang@mail.kib.ac.cn ) Academic editor: Blanca León
© 2022 Yong-Lin Qiu, Ke-Wang Xu, Wen-Bin Ju, Wang-Lin Zhao, Liang 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:
Qiu Y-L, Xu K-W, Ju W-B, Zhao W-L, Zhang L (2022) Hymenasplenium tholiformis (Aspleniaceae), a new fern species from southeastern Xizang, China based on morphological and molecular evidence. PhytoKeys 204: 43-56. https://doi.org/10.3897/phytokeys.204.85746
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A new species of Aspleniaceae, Hymenasplenium tholiformis sp. nov., is described from Medog County in southeastern Xizang, China. The new species is morphologically similar to H. apogamum and H. szechuanense, but the former has ascending pinnae, pinna apex obtuse to rounded, pinna-marginal teeth entire, and veins terminating just below marginal teeth. Phylogenetic analysis based on five plastid markers confirmed that this new species represents a diverging lineage in the H. excisum subclade of Hymenasplenium.
Hymenasplenium, H. excisum subclade, Medog, pinna morphology
Hymenasplenium Hayata is one of two genera in the species-rich fern family Aspleniaceae, comprising more than 60 species worldwide (
Located in southeastern Xizang, Medog County is one of the biodiversity hotspots in China, which has rich plant diversity in the Eastern Himalaya (
Morphological characters of the new species were observed in the field. Herbarium specimens of Hymenasplenium at KUN and PYU were studied. Digital specimens of other related species of Hymenasplenium were examined from the online database CVH (https://www.cvh.ac.cn/) and JSTOR Global Plants (https://plants.jstor.org/). Spore samples were taken from the type specimens and coated with gold particles using the BAL-TEC SCD 005 Cool Sputter Coater (BAL-TECAG., Liechtenstein) and imaged via a QUANTA 200 Scanning Electron Microscope (SEM; FEI Co., USA) at Yunnan University, Kunming, China.
To clarify the phylogenetic position of the new species, we sampled representatives of all the three major clades of the genus and six subclades in the Old World clade (
Total genomic DNA was extracted from silica-gel-dried leaves using the TIANGEN plant genomic DNA extraction kit (TIANGEN Biotech., Beijing, China) following the manufacturers’ protocols. Five plastid markers (atpB, psbA, rbcL, rps4 & rps4-trnS, and trnL & trnL-F) were selected for amplification and sequencing. The PCR system uses the ready-to-use rapid PCR master mix gold Mix (green) 25 μl amplification system developed by Beijing Qingke Xinye Biotechnology Co., Ltd. The new sequences were viewed and edited using Sequencher v.4.14 (Gene Codes Corporation, Ann Arbor, Michigan). The total sequences were automatically aligned in MAFFT ver. 7 (
Like most species in Hymenasplenium, the new species have long-creeping rhizome, once-pinnate laminae, asymmetrical pinnae, reddish-brown rachis, and elliptic to reniform spores, but can be distinguished from other species in the genus by the combined characters of pinna apex obtuse to rounded, ascending pinnae, relatively fewer pairs of pinnae, and pinna-marginal teeth entire, veins terminating just below marginal teeth. The pinna shape of H. tholiformis is most distinct in the genus, with acroscopic margins curved and irregularly toothed, basiscopic margins truncate or slightly curved and entire, and pinna apex obtuse to rounded. A few species in the genus sometimes also have pinna apex obtuse, for example, H. apogamum (N.Murak. & Hatan.) Nakaike, H. szechuanense (Ching) Viane & S.Y. Dong (Table
Comparison of morphological characters to differentiate Hymenasplenium tholiformis, H. szechuanense, H. apogamum, and H. pseudobscurum.
Characters | H. tholiformis | H. szechuanense | H. apogamum | H. pseudobscurum |
---|---|---|---|---|
Size of lamina | 13–16 × 3–5 cm | 15–25 × 3–5 cm | 10–20 × 3–5 cm | 20–25 × 5–10 cm |
Number of lateral pinnae | 15–21 pairs | 20–25 pairs | 15–25 pairs | 15–30 pairs |
Pinna shape | trapeziform to trapeziform-lunate | trapeziform | quadrangular-trapeziform | trapeziform-falcate |
Size of middle pinnae | 2.5–3 × 0.6–1 cm | 1.5–2.3 × 0.7–1 cm | 2–3.5 × 0.6–1 cm | 2.5–4 × 0.8–1.8 cm |
Shape of pinna apex | obtuse to rounded | truncate to obtuse | obtuse to subacute | obtuse to subacute |
Stipe color | shiny, black purple | shiny, dark purple | shiny, purple | not shiny or purple |
Rachis color | purple | purple | purple | grayish green |
Teeth | entire | retuse | entire | entire |
Sori position | medial | inframedial | medial | supramedial |
Indusium | single | single | single | double |
Number of basalveins lacking | 3–4 | 3–4 | 1–2 | 3–5 |
The alignment of five plastid markers was 5,309 bp, of which 3,848 sites were identical, 938 characters were parsimony informative, and 523 variable characters were parsimony-uninformative. A total of 12 sequences are newly generated for this study (Appendix I). The monophyly of Hymenasplenium was confirmed by our reconstructed phylogeny. Hymenasplenium tholiformis was strongly supported as a member of the H. excisum subclade in the Old World clade (
China. Xizang: Medog County, Beibeng Xiang, Xirang, ca. 600 m from the Yarlung Zangbo River, 29°11'17.63"N, 95°03'42.27"E, 720 m elev., 28 Oct 2021, Liang Zhang & Wen-Bin Ju 4781 (holotype: KUN1543824!; isotypes: CDBI!, KUN!).
Hymenasplenium tholiformis is morphologically most similar to H. szechuanense, but different by having larger pinnae (middle pinnae 2.5–3 cm vs. 1.5–2.3 cm), extremely ascending upper pinnae (vs. spreading or slightly ascending), curved margins of acroscopic side of pinnae (vs. truncate), and pinna-marginal teeth entire and veins terminating just below marginal teeth (vs. pinna-marginal teeth retuse to emarginate and veins terminating just below these notches).
Plants perennial, 20–36 cm. Rhizome long-creeping, ca. 2 mm in diam., apex scaly; scales dark brown, lanceolate or narrowly triangular, 0.5–1 × 0.2–0.3 mm, margins entire; roots yellowish brown when dried. Fronds remote, 10–12 mm apart, subglabrous; stipe shiny, black purple, 8–13 cm long, base ca. 2–3 mm in diam., with scales similar to those on rhizome; lamina herbaceous, once pinnate, narrowly oblong to lanceolate, 13–16 × 3–5 cm, base truncate and slightly reduced, apex acuminate to caudate; rachis 0.5–1 mm in diam., wingless, narrowly grooved adaxially, shiny, glabrous, black purple to dark purple; pinnae 15–21 pairs, trapeziform to trapeziform-lunate, basal pinnae nearly opposite, spreading or slightly ascending, upper pinnae alternate, extremely ascending, middle pinnae alternate, ascending, 2.5–3 × 0.6–1 cm, dimidiate, pinna asymmetrical, base largest, upper part of pinna enlarged, similar width as, or slightly wider than, the middle part of pinna, apex obtuse to rounded, acroscopic margins curved and irregularly toothed, teeth entire, basiscopic margins truncate or slightly curved and entire (Fig.
Hymenasplenium tholiformis is endemic to Medog County. Currently, only one large population with ca. 35 individuals was found. According to IUCN Red List criteria B2a or D (
Maximum likelihood phylogeny of Hymenasplenium based on five plastid markers (atpB, psbA, rbcL, rps4 & rps4-trnS, and trnL & trnL-F). The numbers associated with branches are maximum likelihood bootstrap support (MLBS) and Bayesian posterior probability (BIPP). The asterisk indicates MLBS = 100, BIPP = 1.00. The subclades are indicated following
Hymenasplenium tholiformis was observed in a shady place at the bottom of a large rock in the disturbed forest, at an elevation of 720 m, ca. 600 m from the Yarlung Zangbo River. High humidity and cool conditions are important for the growth of the new species.
The specific epithet alludes to dome shape of pinna apex.
yuan ding mo ye tie jiao jue (圆顶膜叶铁角蕨; Chinese name).
In Medog County, ferns are highly diverse along the Yarlung Zangbo River and its tributaries. In this region, at elevations between 650 m and 4500 m, we have discovered four species in three subclades of Hymenasplenium, including H. cheilosorum (Kunze ex Mett.) Tagawa in the H. cheilosorum subclade, H. obliquissimum (Hayata) Sugim. in the H. obliquissimum subclade, and H. excisum and H. tholiformis in the H. excisum subclade. Of the four species, H. tholiformis is distributed at the lowest elevation, while H. obliquissimum is at the highest elevation between 2100 m to 2250 m.
The research was supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502) and the National Natural Science Foundation of China (#32100167). We thank Dr. Bo Xu and Dr. Meng Li for their assistance in the field.
Voucher specimens and GenBank accession numbers for DNA sequences used in this study. Information is presented in the following order: species, voucher, locality, GenBank numbers for rbcL, trnL intron & trnL-F spacer, rps4 & rps4-trnS, atpB, psbA. “*” represents the newly published sequences in this study; “–” no data. Herbaria acronyms follow Index Herbariorum (
Asplenium aegaeum
Lovis, Reichst. & Greuter in Reichst.; Jermy 9181 (BM); Crete; AY300103 (Schneider et al. 2005); AY300050 (Schneider et al. 2005); AY549774 (Schneider et al. 2005); –; –. A. aureum Cav.; Hughes 64 (BM); Belize; AF240651 (Pinter et al. 2002); AF240667 (Pinter et al. 2002); AY549759 (Pinter et al. 2002); –; –. A. cuspidatum Lam.; Grantham & Parsons 0233090 (UC); Costa Rica; AY300111 (Schneider et al. 2004); AY300058 (Schneider et al. 2004); AY549760 (Schneider et al. 2004); –; –. A. dielfalcatum Viane; Wood 7826 (PTBG); Hawaii; AY549738 (Schneider et al. 2005); AY549841 (Schneider et al. 2005); AY549787 (Schneider et al. 2005); –; –. A. erosum Maxon; Unknow; –; KX397706 (Germain-Aubrey,C. C et al., Unpublished); –; –; –; –. A. flabellifolium Cav.; Holmes 4/4/99 (BM); Australia; AY300115 (Schneider et al. 2005); AY300062 (Schneider et al. 2005); AY549779 (Schneider et al. 2005); –; –. A. hastatum Klotzsch ex Kunze; Viane 10182C; Merida, Venezuela; GU929869 (Leroux et al. 2011); –; –; –; –. A. juglandifolium Lam.; Viane 10667; Puerto Rico; GU929870 (Leroux et al. 2011); –; –; –; –. A. normale D. Don; Ohlsen 296 (MELU); Queensland, Australia; KP774926 (Ohlsen et al. 2015); KP851904 (Ohlsen et al. 2015); KP835419 (Ohlsen et al. 2015); –; –. A. polyodon G. Forst; Perrie NC 124 (WELT); New Caledonia; KP774900 (Ohlsen et al. 2015); KP835397 (Ohlsen et al. 2015); KP835433 (Ohlsen et al. 2015); –; –. A. subglandulosum subsp. papaverifolium (Kunze) Salvo, Prada & Consuelo Díaz; Prada & Consuelo Díaz Ohlsen 442 (MELU); Victoria, Australia; KP774929 (Ohlsen et al. 2015); KP851909 (Ohlsen et al. 2015); KP835456 (Ohlsen et al. 2015); –; –. A. tenerum G. Forst; Ohlsen 265 (MELU); Queensland, Australia; KP774858 (Ohlsen et al. 2015); KP835346 (Ohlsen et al. 2015); KP835437 (Ohlsen et al. 2015); –; –. A. trichomanes subsp. inexpectans Lovis; Vogel I-46-B04; France; AY549743 (Schneider et al. 2005); AY549846 (Schneider et al. 2005); AY549792 (Schneider et al. 2005); –; –. A. varians Wall. ex Hook. & Grev.; Fraser-Jenkins 10046–10047 (BM); China; AY300147 (Schneider et al. 2005); AY300094 (Schneider et al. 2005); –; –; –. A. wrightii D. C. Eaton ex Hook.; Cranfill TW040 (UC); Taiwan, China; AY549730 (Schneider et al. 2005); AY549833 (Schneider et al. 2005); AY549766 (Schneider et al. 2005); –; –. A. yunnanense Franch.; Fraser-Jenkins 10044–10045 (BM); China; AY300149 (Schneider et al. 2005); AY300096 (Schneider et al. 2005); AY549803 (Schneider et al. 2005); –; –. Hymenasplenium adiantifrons (Hayata) Viane & S. Y. Dong; Knapp 3609 (P); Taiwan, China; –; MH065559 (Xu et al. 2018); MH065322 (Xu et al. 2018); –; –. H. adiantifrons; Knapp 3904 (P); Taiwan, China; –; MH065560 (Xu et al. 2018); MH065323 (Xu et al. 2018); –; –. H. apogamum N. Murak. & Hatan.; Zhang et al. 7750 (CDBI, MO, VNMN); Thua Thien-Hue, Vietnam; MH065437 (Xu et al. 2018); MH065604 (Xu et al. 2018); MH065376 (Xu et al. 2018); MH065518 (Xu et al. 2018); –. H. apogamum; Chang 1040 (HITBC); Yunnan, China; MH884808 (