Research Article |
Corresponding author: Lian-Ming Gao ( gaolm@mail.kib.ac.cn ) Academic editor: Dennis Stevenson
© 2023 Lian-Ming Gao, Gui-Liang Zhang, Zhi-Qiong Mo, Philip Thomas.
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:
Gao L-M, Zhang G-L, Mo Z-Q, Thomas P (2023) Amentotaxus × hybridia (Taxaceae), a new natural Amentotaxus hybrid from southeast Yunnan province, China. PhytoKeys 226: 101-108. https://doi.org/10.3897/phytokeys.226.103005
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During floristic surveys of Taxaceae in Hekou County, Yunnan Province, China, a putative natural hybrid between A. yunnanensis H.L. Li and A. hekouensis L.M. Gao was collected. Morphological and molecular evidence confirms its status as a natural hybrid. Amentotaxus × hybridia L.M. Gao has linear or linear-lanceolate leaves 6–13 cm × 1.0–1.5 cm, white stomatal bands with 34–40 rows on abaxial side, 2.5–3.5 mm, slightly wider than leaf margins; 3–6 seeds borne at the base of the branchlet, peduncle 1.3–1.6 cm long with 3–4 rows of persistent basal bracts.
Amentotaxus × hybridia, molecular evidence, natural hybridisation, new hybrid, Taxaceae
The genus Amentotaxus Pilg. (1916) in the family Taxaceae comprises five or six species (
In February 2016, surveys were undertaken in the mountains near Nanxi town, Hekou county, Yunnan province, China to collect fertile material of the recently described species Ametotaxus hekouensis L.M. Gao. This taxon was initially identified as a potential new species based on DNA barcoding data (
All measurements of the new hybrid of Amentotaxus were taken from dried herbarium specimens of the hybrid individual GLM164267. All measurements of A. hekouensis and A. yunnanensis were based on literature (
To confirm that the individual (GLM164267) is a hybrid between A. hekouensis and A. yunnanensis, we generated approximately 2.5GB (gigabase) of genome skimming data to assemble the complete plastid genome and nrITS region. The methods of DNA extraction, genome skimming sequencing, the plastome and nrITS sequences assembly, and gene annotation are detailed in
The morphological trait comparison among the three taxa showed that several traits of the hybrid (Amentotaxus × hybridia), such as texture of leaves, width of stomatal bands, and number of rows of each stomatal band, are intermediate between A. hekouensis and A. yunnanensis, but with more similarity to A. hekouensis. The hybrid differs from its parental species by having linear or linear-lanceolate leaves, white stomatal bands with 34–40 rows that are slightly wider than the marginal bands in width; 3–6 seeds borne at the base of the branchlet, and 3–4 rows of persistent basal bracts at the peduncle (Table
Characters | A. hekouensis | A. × hybridia | A. yunnanensis |
---|---|---|---|
Leaf Length (cm) | 8–12.5 cm | 6–13 cm | 3.5–10 cm |
Leaf width (cm) | 9–14 mm | 10–15 mm | 8–12 mm |
Leaf texture | thin, leathery | moderately thick, leathery | thick, leathery |
Leaf apex | long acuminate | acuminate | obtuse or tapered |
Width of stomatal bands | 2.1–3.0 mm | 2.5–3.5 mm | 3–4 mm |
No. rows of each stomatal band | 25–30 | 34–40 | c. 40 |
Ratio of stomatal band/marginal band | 0.75–1 | 1.10–1.25 | > 2 |
Marginal band colour in fresh leaves | bright green | green | yellowish green |
No. of bract rows on peduncle | unknown | 3–4 | 2 |
The nrITS sequence of the hybrid individual de novo was assembled using the GetOrganelle toolkit (
Sequence variation and polymorphisms of nrITS among the parent species and the hybrid.
nrITS | ITS1 | ITS2 | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Position | 179 | 200 | 268 | 307 | 355 | 366 | 368 | 425 | 461 | 516 | 816 | 833 | 856 | 861 | 910 | 964 | 969 |
A. yunnanensis AM21 (female) | C | T | G | T | C | A | G | T | G | T | C | C | T | G | C | T | C |
A. hekouensis AM24 (male) | T | C | A | C | T | T | T | C | C | C | T | – | C | A | G | – | G |
A. × hybridia AM51 | T/C | C/T | A/G | C/T | T/C | T/A | T/G | C/T | C/G | C/T | T/C | -/C | C/T | A/G | G/C | -/T | G/C |
Nucleotide rate of polymorphic mapping sites# | 2.0 | 2.2 | 2.2 | 2.3 | 2.5 | 2.0 | 2.0 | 2.1 | 2.2 | 2.3 | 3.2 | 2.6 | 2.6 | 2.1 | 2.0 | 1.9 | 1.7 |
The length of the plastome of the hybrid (GLM164267) is 137,786 bp with 35.8% GC content. A total of 198,855 reads were mapped to the assembled plastome with an average sequencing coverage of 215×. The whole plastome included 118 unique genes, comprising 4 rRNA genes, 31 tRNA genes (three tRNA have two copies: trnI-CAU, trnN-GUU and trnQ-UUG) and 83 protein-coding genes. The plastid genome phylogenetic tree of Amentotaxus showed that the hybrid individual fell in the clade of A. hekouensis (data not shown). As the plastid genome is paternally inherited in Amentotaxus, the results demonstrate that A. hekouensis is the paternal parent with A. yunnanensis as the maternal parent. In our previous DNA barcoding study (
Amentotaxus × hybridia L.M. Gao & G.L. Zhang resembles A. hekouensis L.M. Gao, but differs by its larger linear or linear-lanceolate leaves of 6–13 cm × 1.0–1.5 cm, stomatal bands with 34–40 rows on abaxial side, 2.5–3.5 mm wide, slightly wider than the green leaf margins; 3–6 seeds borne at the base of the branchlets, peduncle 1.3–1.6 cm long, 3–4 rows of persistent basal bracts (Table
China. Yunnan: Qincaitang Mt., Longbao village, Nanxi Town, Hekou County, Honghe, 22°39'49"N, 104°01'17"E, elevation 1100 m, 15 February 2016 (with mature seeds), Zhang GL, GLM164267 (Holotype: KUN, isotype: KUN).
Small tree up to 5 m tall, bark brown gray; branch cylindric or subtetragonal, yellowish green; leafy branchlets ascending, broadly rectangular to oblong-elliptic in outline, axis green in 1st year, greenish yellow in 2nd and 3rd years, quadrangular or subterete in cross section. Leaves borne at 40–70° to the branchlet axis, distichous, twisted at the short petiolate or nearly sessile base, subsessile or petiolate, petiole to 2 mm long, almost opposite, 5–7 leaf pairs on each branchlet; Leaves leathery, linear or linear-lanceolate, 6–13 cm × 1.0–1.5 cm, straight, sometimes slightly falcate, cuneate at base, asymmetric, apex acuminate, leaf margin narrowly revolute, sometime flat; leaf marginal band green when fresh, yellowish green when dry, 2.0–3.0 mm wide; stomatal bands white when fresh and yellow white when dry, 2.5–3.5 mm wide, slightly wider than green leaf margins, stomata in 34–40 rows of each band, densely arranged; midvein slightly sunken or flat adaxially, raised abaxially, 1.5–2.0 mm wide, narrower than the stomatal and marginal bands, yellowish green, same color as the branchlet. Seed-bearing structures in clusters of 3–6 at the base of the branchlet, not from subtending leaf. Aril reddish purple when ripe. Mature seed reddish purple, obovoid-ellipsoid, 2.5–3.0 cm × 1.4–1.6 cm, mucronate at apex, naked; peduncle 1.3–1.6 cm long, compressed-quadrangular, slightly dilated below bracts; 3–4 rows of persistent basal bracts on peduncle, four bracts per row, imbricate, obovate or obovate-oblong, with a ridge in middle. Seed maturity February. Pollen cone not seen.
Amentotaxus × hybridia has only been found in the karst montane monsoon evergreen forest in southeast Yunnan province along the border between China (Hekou, Yunnan) and Vietnam occurring at an elevation around 1100 m.
Seed matures in February.
The specific epithet is derived from the natural hybridisation between A. yunnanensis and A. hekouensis.
As a natural hybrid, Amentotaxus × hybridia is not eligible for listing under the current IUCN Categories and Criteria (
We are grateful to Ms. Ling Wang from KUN for drawing the illustration of the holotype. This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31000000) and the Key Basic Research Program of Yunnan Province, China (202101BC070003). The Royal Botanic Garden Edinburgh is funded by the Rural and Environment Science and Analytical Services division of the Scottish Government.