Research Article |
Corresponding author: Zheng-Yu Zuo ( zuozhengyu@mail.kib.ac.cn ) Academic editor: Joel Nitta
© 2024 Hong-Jin Wei, Zheng-Yu Zuo.
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:
Wei H-J, Zuo Z-Y (2024) Dryopteris × subdiffracta (Dryopteridaceae), a new natural hybrid fern from Guangxi, China. PhytoKeys 250: 7-19. https://doi.org/10.3897/phytokeys.250.119803
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A new natural hybrid fern, Dryopteris × subdiffracta (Dryopteridaceae), is reported from Guangxi, China. Molecular phylogenetic analysis based on DNA sequences from the low-copy nuclear marker Ak1 and plastid genome revealed respectively that D. polita and D. diffracta are parents of the new hybrid, with D. polita as the maternal parent. Cytometric analysis of the nuclear DNA content indicated that D. × subdiffracta might be a diploid hybrid. Morphologically, D. × subdiffracta shares a high degree of similarity with D. × subreflexipinna from Taiwan, especially in zigzag-shaped rachis and deflexed pinna stalks. However, D. × subdiffracta is distinguishable in the degree of lamina division and shapes of lamina and pinnulets. A comprehensive taxonomic description accompanied by line drawings are provided.
Dryopteris sect. Acrorumohra, hybridization, molecular phylogeny, nuclear gene AK1, plastome
Dryopteris Adans. (1763: 20) is the third largest genus of ferns worldwide, comprising about 400 species (
In 2018, a suspicious fern was collected in the Dayaoshan Mountains, the largest mountain in the east-center of Guangxi, China. This fern bears a striking resemblance to Dryopteris × subreflexipinna M.
Samples included Dryopteris × subdiffracta and its two associated species (i.e., supposed parents), D. diffracta and D. polita, collected at the same location. Additionally, D. hasseltii, the maternal progenitor of D. × subreflexipinna (
Plastid DNA was used as the maternal inherited marker and AK1 as a biparentally inherited low-copy nuclear marker. Total DNA was extracted using an improved extraction CTAB method (
Taxon, voucher specimen information, GenBank accession numbers, nuclear DNA content, and the number of spores per sporangium of Dryopteris samples used in this study.
Taxon | Specimen | Locality | Plastome | AK1 copies | pg/2C | Spores | Ploidy |
---|---|---|---|---|---|---|---|
D. diffracta | JSL6261 | Jinxiu, Guangxi, China | PQ167731 | PP277076 | |||
D. diffracta | Zuo1817 | Gongshan, Yunnan, China | OQ649848 | PP277077 | 19.49 ± 0.54 | 64 | 2× |
D. diffracta | Zuo5590 | Jinxiu, Guangxi, China | PQ167732 | PP277078 | 20.20 ± 0.71 | 64 | 2× |
D. hasseltii | DLJ2019235 | Gongshan, Yunnan, China | OQ649872 | PP277079 | 20.08 ± 0.15 | 64 | 2× |
D. polita | JSL6338 | Jinxiu, Guangxi, China | PQ167733 | PP277082 | |||
D. polita | Zuo5577 | Jinxiu, Guangxi, China | PQ167734 | PP277083 | 14.65 ± 0.32 | 64 | 2× |
D. × subdiffracta | JSL6337 | Jinxiu, Guangxi, China | PQ167735 | PP277084; PP277085 | |||
D. × subdiffracta | JSL6341 | Jinxiu, Guangxi, China | PQ167736 | PP277086; PP277087 | |||
D. × subdiffracta | Zuo5589 | Jinxiu, Guangxi, China | PQ167737 | PP277088; PP277089 | 16.82 ± 0.17 | 2× |
Two matrices were constructed for the analyses. The first matrix (plastid matrix) was comprised of nine entire chloroplast genome using Geneious 9.1.4 (
Flow cytometry was employed to measure the nuclear DNA content (2C value) of individual cells extracted from fresh leaves (
Morphological differences (marked with asterisk “*”) and similarities between Dryopteris × subdiffracta and D. × subreflexipinna are listed in Table
Morphological comparison between Dryopteris × subdiffracta and D. × subreflexipinna.
Characters | D. × subdiffracta | D. × subreflexipinna | |
---|---|---|---|
Scales | color | brown | brown |
shape | lanceolate | lanceolate | |
margin | entire | entire | |
Frond length* | 42–99 cm | 65–123 cm | |
Lamina | division* | tripinnate to tripinnate-pinnatisect | 4-pinnate |
shape* | triangular or ovate-triangular | ovate-oblong or ovate | |
size* | 22–44 × 15–34 cm | 25–66 × 22–50 cm | |
base | broadly cuneate* or rounded | rounded | |
Rachis form | slightly zigzag | slightly zigzag | |
Shape of lowest pinna | deltoid | deltoid | |
Included angle between rachis and deflexed pinna stalk | 70–85° | 70–85° | |
Size of basal basiscopic pinnule on lowest pinna* | 36–90 × 17–37 mm | 45–180 × 22–80 mm | |
Middle pinnules of pinnae | shape | deltoid-lanceolate | oblong-lanceolate* or deltoid-lanceolate. |
base* | nearly symmetrical; broadly cuneate acroscopically, broadly cuneate to cuneate basiscopically. | asymmetrical; truncate acroscopically, broadly cuneate to cuneate basiscopically. | |
apex | shortly acuminate | shortly acuminate, acute or obtuse* | |
Pinnulets nonadjacent to costae | shape* | ovate to ovate-oblong | rhombic-ovate |
base* | cuneate to rounded-cuneate, nearly symmetrical | rounded-cuneate, asymmetrical | |
apex | blunt* or obtuse | rounded* or obtuse | |
Relative size of proximal pair of pinnulets)* | acroscopic one nearly as large as or slightly larger than basiscopic one | acroscopic one significantly larger than basiscopic one | |
Relative size of proximal pair of ultimate pinnules (or lobes)* | acroscopic one nearly as large as or slightly larger than basiscopic one | acroscopic one significantly larger than basiscopic one |
Phylogenetic analysis of the plastid matrix showed that three samples of Dryopteris × subdiffracta were fully supported to nest in the clade of D. polita (Fig.
The mean DNA contents of D. × subdiffracta and related species are presented in Table
All the samples of D. diffracta, D. hasseltii and D. polita were observed with 64 spores per sporangium and considered to be sexual. The DNA content of samples of D. × subdiffracta was 16.82 ± 0.17 pg, and these samples were also estimated as being diploid. Most of sporangia of D. × subdiffracta were abortive. Some sporangia had a few normal spores occasionally, but most of these spores were misshapen (Fig.
Dryopteris × subdiffracta A pinnules showing fertile sori (blue arrow) and infertile sori (red arrows) B sporangium showing mostly misshapen spores (red arrow) and a few normal spores (blue arrow), insets (circles) show detail. Photographed by Zheng-Yu Zuo. Scale bars: (in circles) 0.05 mm.
Maximum likelihood phylogram of Dryopteris sect. Acrorumohra based on (A) plastid matrix and (B) nuclear AK1 gene sequences. Support values, including bootstrap support values (BS) and Bayesian confidence values (PP), are depicted along the branches, with PP over the branches and BS under the branches. The NCBI accession numbers of sequences obtained from GenBank are given after the taxon names.
Previous studies reported that Dryopteris × subreflexipinna is a pentaploid hybrid produced from hybridization between diploid sexual D. hasseltii and tetraploid apogamous D. diffracta (
≡ D. diffracta (Baker) C. Chr. × D. polita Rosenst.
China • Guangxi: Jinxiu county, Mt. Shengtangshan, in broad-leaved forest, 23°58'11"N, 116°6'54"E, elev. 1156 m, 9 May 2018, She-Lang Jin, Jing Liu, Qi-MingTang & Xu Yan JSL6337 (holotype: CSH0200999!; isotypes: CSH!,
Dryopteris × subdiffracta is similar to D. × subreflexipinna in having slightly flexuous rachis and deflexed pinna stalks, but the former has a tripinnate to tripinnate-pinnatisect frond, narrowly ovate or oblong pinnulets with obtuse apex and nearly symmetric base, while the latter has 4-pinnate frond, ovate pinnulets with round or obtuse-rounded apex and asymmetric base.
Dryopteris × subdiffracta A habitat showing the plant growing together with parents (arrows inset) B Dryopteris diffracta and D. polita C adaxial view of lamina D habit E abaxial view of lamina F adaxial view of lower portion of middle pinna with portion of rachis G adaxial view of lower portion of middle pinna with portion of rachis H ultimate pinnule I sori J indusium K adaxial view of portion of rachis with lower portion of costae L rhizome with lower portion of stipes. Photographed by Hong-Jin Wei.
Rhizome erect, densely covered with brown scales at apex. Frond (42–)50–84 cm; stipe stramineous, (23–)26–56 cm, (1–)1.5–3 mm in diam. at middle part, sparsely covered with scale at base, upwards glabrous, grooved adaxially; scales lanceolate, ca. 16 × 2.4 mm, brown, entire; lamina 3-pinnate to nearly 4-pinnate, deltoid to ovate-deltoid, (22–)27–43 × (15–)25–34 cm, base round or broadly cuneate, apex acuminate, rachis somewhat flexuous; pinnae 8–12 pairs, triangular-lanceolate, slightly falcate, alternate, lowest pair sometimes opposite to nearly opposite, stalked, stalks of lower pinnae slightly deflexed, bases forming an angle of ca. 70–85° with rachis, upswept distally, 2–6.5 cm apart from each other, stalks of middle pinnae spreading; lowest pinna largest, deltoid, (9–)12–21 × (6–)7–13 cm, base broadly cuneate or truncate, apex acuminate, stalk (1.5–)2–4 cm; pinnules 8–12 pairs, often anadromous, 1- or 2-pinnate, alternate, spreading, triangular-lanceolate, apex shortly acuminate, proximal pairs shortly stalked, bases broadly cuneate or shallowly cordate, nearly symmetrical, distal pairs of pinnules nearly sessile, bases asymmetrical, acroscopically broadly cuneate, basiscopically cuneate, basal acroscopic pinnule of pinna as large as or slightly smaller than adjacent ones, basal basiscopic pinnule on lowest pinna largest, (3.6–)5.5–7.5(–9) × (1.7–)2–3.7 cm, shortly acuminate, stalklet (1.5–)2–4 mm; pinnulets 6–10 pairs, often anadromous, proximal 2–5 pairs free, alternate, spreading to ascending, ovate to ovate-oblong, basal acroscopic one as large as or slightly larger than basiscopic one, bases of proximal pair rounded-cuneate, nearly symmetrical, bases of others rounded-cuneate to cuneate acroscopically, cuneate to narrowly cuneate basiscopically, apex blunt, acute to subacute, with 1 or 2 short obtuse teeth, larger pinnules (9.5–)11–18 × (5.5–)6.5–11 mm, stalklet 0.5–2 mm, pinnatifid or pinnatisect at base, with 1 or 2 free lobes proximally; lobes 1–3 pairs, ovate, narrowly ovate or oblong, ascending, margin undulant to entire, base narrowly cuneate, apex obtuse, entire or with 1 or 2 short obtuse teeth, larger lobes 3–6 × 2–3 mm; upper pinnae gradually reduced, spreading to oblique; lamina herbaceous, green on adaxial surface and light green on abaxial surface when dry, both surfaces glabrous, rachis and rachillae of every order stramineous, nearly glabrous expect for several hair-like scales on midribs and rachillae on abaxial surface, grooved adaxially; veins indistinct on adaxial surface, visible on abaxial surface, pinnate on pinnulets, veinlets forked or simple on lobes, not reaching margin; sori medial or slightly nearer to margin than to costa, terminal on veinlets, 1–3 pairs on each ultimate lobes; indusium brown, papery, entire, fugacious.
Dryopteris × subdiffracta was found in Jinxiu, Shangling and Wumin County, Guangxi Zhuang Autonomous Region, South China (Fig.
We noticed that two specimens of D. × subreflexipinna (TAI270081, TAI270101) collected from Taiwan are consistent with the characteristics of the new hybrid. There is a strong possibility that these two specimens were collected in the area where D. diffracta coexisted with D. polita. Dryopteris × subdiffracta might be distributed to Taiwan.
The specific name is derived from the Latin prefix sub- (close to), and diffracta, epitheton of a species, referring the new species is closely related to Dryopteris diffracta.
曲轴鳞毛蕨 (qū zhóu lín máo jué).
China • Guangxi: Same place as the holotype, 1100–1200 m, 9 May 2018, She-Lang Jin, Jing Liu, Qi-MingTang & Xu Yan JSL6341 (CSH!), Jing Liu, She-Lang Jin, Qi-MingTang & Xu Yan DYS426, DYS427, DYS428 (
China • Guangxi: Wumin County, Mt. Damingshan, Gannanhe (Ganlanhe), elev. 800–1000 m, 14 Sep. 1991, Hou-Gao Zhou & Hua Li 2769 (
We would like to thank Zhao-Cen Lu and other staffs in Herbarium of Guangxi Institute of Botany for providing information about the specimens used in this study.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This study is partly supported by the Postdoctoral Directional Training Foundation of Yunnan Province and the National Wild Plant Germplasm Resource Center for Shanghai Chenshan Botanical Garden (#ZWGX2302).
Conceptualization: HJW, ZYZ. Investigation: HJW, ZYZ. Funding acquisition: ZYZ. Methodology: ZYZ. Software: ZYZ. Supervision: ZYZ. Writing - original draft: HJW, ZYZ. Writing - review and editing: HJW, ZYZ.
Hong-Jin Wei https://orcid.org/0000-0002-3679-6683
Zheng-Yu Zuo https://orcid.org/0000-0002-8334-6132
All of the data that support the findings of this study are available in the main text.