Ophioglossum hongii M. Y. Li, F. S. Yang & J. P. Shu, 2024

Li, Min-Yu, Yang, Fu-Sheng, Yan, Yue-Hong, Chen, Li-Jun, Huang, Zhi-Cong, Shu, Jiang- Ping & Qin, Xin-Sheng, 2024, Ophioglossum hongii (Ophioglossaceae), a new species from Xizang, China, Phytotaxa 676 (2), pp. 169-180 : 171-175

Ophioglossum hongii M. Y. Li, F. S. Yang & J. P. Shu sp. nov. ( Figs 1–2 )

Type:— CHINA. Xizang Autonomous Region, Shannan City , Gongga County, 29°17′12.79″N, 90°59′30.14″E, ca. 3568 m, 13 Aug 2021, F. S. Yang YYH22612 (holotype: NOCC!; isotype: PE!) .

Diagnosis:— Ophioglossum hongii resembles O. polyphyllum , but differs in its smaller size, ovate-elliptic or elongate-elliptic trophophyll (vs narrowly elliptic to oblong lanceolate), 1.2–2 cm long fertile stalk (vs 3–6 cm) and spores with granular tubercles forming a densely reticulate ridge on the distal face (vs zigzag plates often mixed up forming smaller gaps among ridges and furrows on the distal face)

Plants less than 10 cm, terrestrial; rhizome subterranean, cylindrical, yellow-brown, bearing numerous fleshy roots; common stalk 2.5–4.5 cm long, terranean-subterranean, white when subterranean, green when terranean, glabrous, covered with persistent brown petiole at base; trophophylls born close to the ground, concave from above, 1.5–3.5 cm long, 0.8–1.2 cm broad, 1–2(–3) per rhizome, ovate-elliptic or elongate-elliptic, mucro at apex, cuneate at base, margins entire, dark green, glabrous, texture subfleshy; venation reticulate, indistinct; fertile segment 2–3.5 cm long, round-flat, arising from base of trophophyll lamina; strobili 0.8–2 cm long, thick, apex apicalute, green when young, yellow when mature; sporangia 10–20 on either side; spores triradiate, globose, equatorial diameter 40–45 µm, granular tubercles forming a densely reticulate ridge on distal face, irregular tubercles with scattered micro perforation on proximal face.

Etymology:— The specific epithet is chosen to honour Professor De-Yuan Hong for his outstanding contribution to the compilation of Flora of Pan Himalaya.

Phenology:— Ophioglossum hongii was observed at fertile phase between July and October.

Distribution & Ecology:— Ophioglossum hongii was found growing on soil in sparse shrubland at elevation ca. 3000–4000 m in the plateau region of southwestern China.

Conservation status:— Ophioglossum hongii is currently recorded from three locations: Xizang Autonomous Region, Sichuan, and Yunnan provinces in China. Based on predictions of the potential suitable distribution areas of O. hongii under current climatic conditions, the main environmental factors influencing species distribution are Elevation and Isothermality, with a combined contribution of up to 63.3%. The highly suitable areas cover 100,380 km 2, mainly concentrated in the plateau regions of three provinces ( Fig. 3 ), which roughly correspond to the natural distribution areas. According to the International Union for Conservation of Nature categories and criteria ( IUCN 2024), O. hongii is widespread with stable populations and minimal human interference, thereby qualifying it for the Least Concern (LC) classification.

Taxonomic notes:— Some specimens of Ophioglossum hongii have been misidentified as O. nudicaule due to their similar plant size and trophophyll morphology. But the conspicuous persistent petiole bases at the top of rhizome, shorter sporophores and molecular results indicated the distinctness of the new species from O. nudicaule ( Fig. 4 ). It may also be confused with O. polyphyllum because they are similar in having the conspicuous persistent petiole bases, but it can be distinguished by the trophophyll shape, which is ovate-elliptic or elongate-elliptic in O. hongii and narrowly elliptic to oblong lanceolate in O. polyphyllum . In addition, O. hongii has 1.2–2 cm long fertile stalk versus 3–6 cm in O. polyphyllum . The spore ornamentation with granular tubercles forming a densely reticulate ridge on distal face in O. hongii versus zigzag plates often mixed up forming smaller gaps among ridges and furrows on distal face in O. polyphyllum ( Patel & Narsimha Reddy 2019) . A detailed morphological comparison is provided in Table 1.

Additional specimen examined (paratype):— CHINA, Xizang Autonomous Region: Shannan, Gongga, 13 Aug 2021, F. S. Yang PE-YANGFS2021-412 ( PE) ; Changdu, Gongjue, 22 Aug 1976, Qinghai-Tibet Team Vegetation Group 9717 ( PE) ; Rikaze, Angren, 13Aug 1961, Zhang J. W. 2703 ( PE) ; Shannan, Jiacha , 29°3′56″N, 92°42′51″W, 8 Oct 2010, Xu B. Q. & Tong Y. H. XiaNh-07zx-0657 ( IBSC) ; Linzhi, Chayu, Sacred mt. Kar-war kar-boo, Tsa-wa rung, Sept 1935, Wang Q. W. 66236 ( NAS) ; Lasa, Chengguan District, Lhalu Wetland Reserve , 29°41′21.3″N, 91°6′37.6″W, 15 Aug 2020, Zhu X.X. et al. ZXX201765 ( KUN). Sichuan Province: Ganzi Tibetan Autonomous Prefecture, Daofu, 16 Aug 1960, Sichuan Pharmaceutical Source Census Team 15532 ( NAS) ; Aba Tibetan and Qiang Autonomous Prefecture, Maerkang, 18 July 1960, Sichuan Pharmaceutical Source Census Team 22092 ( NAS) ; Ganzi Tibetan Autonomous Prefecture, Xiangcheng, 31 July 1981, Qinghai-Tibet Team 3115 ( PE). Yunnan Province: Diqing Tibetan Autonomous Prefecture, Deqin, Feilai Monastery, 8 Aug 2018, Hu J. et al. SC-a-074- B26 ( NAS) .

Phylogenetic analysis:— In the phylogenetic tree of seven chloroplast DNA sequences (atpB, matK, psbA-trnH, rbcL, rps4, rps4-trnS, and trnL-F), O. hongii is clustered with O. polyphyllum and O. engelmannii in a monophyletic clade. Additionally, two samples of O. hongii are recovered as a separate lineage, sister to the clade composed of O. polyphyllum and O. engelmannii with 100% support ( Fig. 4 ).

Chloroplast genome:— The complete chloroplast genome sequence of Ophioglossum hongii was 135,126 bp in length with a GC content of 41.4%, and showed a typical quadripartite structure ( Fig. 5 ), comprising a pair of inverted repeats (IR) regions of 19,928 bp each, a large single-copy (LSC) region of 95,906 bp, and a small single-copy (SSC) region of 19,292 bp. A total of 129 genes were annotated, including 84 protein-coding genes, 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. Additionally, 10 cis-splicing genes including ndhB, atpF, rpoC1, ycf3, clpP, petB, petD, rpl16, rpl2, and ndhA were detected.

Figures

FIGURE 1. Ophioglossum hongii M. Y. Li, F. S. Yang & J. P. Shu sp. nov. (A) habit, (B) detail of spike, (C) spores.

FIGURE 2. Ophioglossum hongii sp. nov. (Ophioglossaceae) from Xizang Autonomous Region, China. (A–B) Habitat, (C) Trophophylls, (D) Sporophore, (E) Rhizome and Roots, (F) SEM photomicrographs of spore distal view, (G) SEM photomicrographs of spore proximal view. Photo by Xin-Xin Zhu (C–E) & Jiao He (F–G).

FIGURE 3. Distribution map and prediction of potential suitable distribution for O. hongii in China.

FIGURE 4. Maximum-likelihood phylogenetic tree of Ophioglossaceae based on seven plastid regions. The number on each node indicates the bootstrap support (BS) values (>50%). The new sequences are shown in thick font. Voucher information is indicated in blue. Geographical provenances are indicated in green.

FIGURE 5. Chloroplast genome map of Ophioglossum hongii. Genes on the inner side of the circle undergo transcription in a clockwise direction, while those on the outer side are transcribed in a counterclockwise direction. The inner circle, represented in dark gray, corresponds to the GC content, whereas the light gray denotes the content. Diverse colors symbolize different functional genes. The pronounced line on the large circle delineates the boundaries of the inverted repeat regions (IRA and IRB), segregating the genome into small single-copy (SSC) and large single-copy (LSC) regions.