Research Article |
Corresponding author: Nguyen Van Ngoc ( mr.ngocnv@gmail.com ) Academic editor: Norbert Holstein
© 2022 Nguyen Van Ngoc, Hoang Thi Binh, Hoang Thanh Son, Yoshihisa Suyama, Tetsukazu Yahara.
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:
Ngoc NV, Binh HT, Son HT, Suyama Y, Yahara T (2022) A new species of Quercus genus (Fagaceae) from Son Tra Peninsula, Central Vietnam. PhytoKeys 206: 61-73. https://doi.org/10.3897/phytokeys.206.85635
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A new species, Quercus sontraensis Ngoc, Binh & Son is described from Son Tra Nature Reserve, Son Tra Peninsula, Central Vietnam. We examined the morphology and constructed a highly resolved phylogeny of Q. sontraensis and its relatives (including Q. langbianensis and Q. cambodiensis) using Multiplex ISSR genotyping by sequencing (MIG-seq). The morphological analyses and molecular evidence support the distinction between the new species (Q. sontraensis) and its relatives.
Da Nang City, flora, MIG-seq, phylogeny, taxonomy
The genus Quercus contains more than 500 species worldwide, amongst which about 400 species from the Americas, Europe, North Africa and Macaronesia and about 125 species were reported from Asia (
Son Tra Nature Reserve is located on the Son Tra Peninsula of Da Nang City (Fig.
During a field excursion to the Son Tra Nature Reserve carried out in 2016 and 2019, we collected specimens of Quercus from 340 m to 430 m altitude, which we were unable to allocate to a described species. Further studies, based on specimens in the herbaria such as DLU, FU, HN, P and VNM, the digitised specimen images on the website of JSTOR Global Plants and literature on related species (
By combining the molecular evidence and morphological observations, we describe and illustrate the unknown species from Son Tra as Quercus sontraensis Ngoc, Binh & Son. Additionally, this study used Multiplex ISSR genotyping by sequencing (MIG-seq:
A total of fifteen samples of Quercus from Vietnam and Cambodia including, Q. sontraensis and its related species, were collected for molecular analysis. Three samples of L. dahuoaiensis, L. vuquangensis and L. vinhensis were included as an outgroup in the inference of the phylogenetic tree. The information on samples used for molecular analysis in this study is shown in Table
Country | Area | Voucher | Elevation | Species |
---|---|---|---|---|
Vietnam | Lam Dong | V9723 | 1930 m | Quercus lanata |
Lam Dong | V3172 | 890 m | Q. setulosa | |
Cao Bang | V6066 | 767 m | Q. trungkhanhensis | |
Da Nang | V3156 | 340 m | Q. austrocochinchinensis | |
Da Nang | V3113 | 1310 m | Q. poilanei | |
Lam Dong | V10132 | 1630 m | Q. poilanei | |
Lam Dong | V9884 | 1637 m | Q. braianensis | |
Lam Dong | V4445 | 1464 m | Q. braianensis | |
Lam Dong | V10069 | 1867 m | Q. bidoupensis | |
Lam Dong | V10090 | 1884 m | Q. bidoupensis | |
Lam Dong | V5537 | N/A | Q. djiringensis | |
Lam Dong | V10061 | 1867 m | Q. langbianensis | |
Lam Dong | V9972 | 1430 m | Q. langbianensis | |
Da Nang | QC201 | 340 m | Q. sontraensis | |
Ha Tinh | V5743 | 1518 m | L. vuquangensis | |
Nghe An | V3787 | 1062 m | L. vinhensis | |
Lam Dong | V3194 | 225 m | L. dahuoaiensis | |
Cambodia | Bokor | C4302 | 844 m | Q. cambodiensis |
In addition, the following specimen vouchers of Q. cambodiensis: Poilane 215 (P [P00379257, P00379258] and NY [NY00253790]), Poilane 270 (P [P06872434, P06872435]), Tagane et al. C4302 (FU) and Toyama et al. 1834 (FU), the following specimen vouchers of Q. langbianensis: Chevalier 30029 (P [P00379254, P00379255, P00379256]), Tagane et al. V4465, V4165, V4166, V3962 (DLU, FU) and the following specimen vouchers of Q. sontraensis: Son et al. QC201 (DLU, VAFS: three duplicates), Son H.T. QC202 (DLU, VAFS: two duplicates) and Son H.T. QC203 (DLU, VAFS) were selected to measure the key morphological characters in the morphological analysis (a total 33 leaf of each species were measured).
To identify new samples that were collected from Son Tra Nature Reserve (Fig.
Additionally, to provide strong evidence for the new species, we analysed and compared several key morphological characteristics including petiole length, leaf blade length and width and leaf blade aspect ratio, based on specimens of the new species and its related species. We used ImageJ (
To evaluate differences amongst species, analysis of variance (ANOVA) and Game-Howell post hoc test (
For DNA extraction, we used the dried leaf material and milled them into fine powder with a QIAGEN TissueLyser. Then the powder was washed three times by 1 ml buffer solution (comprising 0.1 M HEPES, pH 8.0; 2% Mercaptoethanol; 1% PVP; 0.05% Ascorbic acid) (
Fifteen DNA samples of eleven Quercus species were used to amplify thousands of short sequences by using the primers of “multiplexed ISSR genotyping by sequencing” (MIG-seq:
The raw data of DNA sequence were pretreated following the published protocol (
Quercus sontraensis is morphologically most similar to Q. cambodiensis Hickel & A.Camus and Q. langbianensis Hickel & A.Camus. The comparison of key morphological characters amongst Q. sontraensis, Q. cambodiensis and Q. langbianensis are shown in Tables
Morphological comparison amongst Quercus sontraensis Binh, Ngoc & Son, sp. nov., Quercus cambodiensis Hickel & A.Camus and Quercus langbianensis Hickel & A.Camus.
Characters | Q. sontraensis | Q. cambodiensis (1,2,3) | Q. langbianensis (4,5,6) |
---|---|---|---|
Young shoot | Curly golden hairy | Golden tomentose | Golden tomentose |
Leaf margin | Regularly and distinctly serrate on upper 1/3–1/4(–1/5) | Almost entire or with a few low teeth in upper 1/4 | Distinctly serrate in upper 1/3 |
Length of petioles | (0.7–)1–1.5 cm | 1–2.2 cm | 1–2 cm |
Number of secondary veins | (8–)11–14 pairs | 7–11 pairs | 10–12 pairs |
Infructescence | Each infructescence with 1–3 acorns | Each infructescence with 4 acorns | Each infructescence with 2 acorns |
Cupule shape | Bowl-shaped | Cup-shaped | Cup-shaped |
Number of rings on cupule | 7–8 rings | 7–8 rings | 6–9 rings |
Margin of rings on cupule | Distinctly toothed in all rings, except two upper rings | Distinctly toothed in two lower rings | Distinctly toothed in all rings |
Nut enclosure by cupule | Enclosing 1/3 of the nut | Enclosing < 1/2 of the nut | Enclosing 1/3 of the nut |
Nut shape | Broadly ellipsoid | Obovoid to ellipsoid | Obovoid to ellipsoid |
Base of the nut | Slightly convex | Slightly convex | Convex |
According to the original description of Q. cambodiensis,
The morphological comparison of leaf traits amongst Q. sontraensis and Q. cambodiensis and Q. langbianensis (Table
The comparisons of mean (X) and standard deviation (SD) value of the leaf blade amongst Quercus sontraensis, Q. cambodiensis and Q. langbianensis. 1Derived from type specimens, 2Derived from our collections, n = number of leaves measured in this study.
Parameters | Q. sontraensis 1 | Q. langbianensis 1,2 | Q. cambodiensis 1,2 | ||||||
---|---|---|---|---|---|---|---|---|---|
X | SD | n | X | SD | n | X | SD | n | |
Leaf blade length (cm) | 9.27 | 1.93 | 33 | 10.54 | 2.02 | 33 | 7.76 | 2.25 | 33 |
Leaf blade width (cm) | 2.89 | 0.59 | 33 | 3.77 | 0.80 | 33 | 2.57 | 0.66 | 33 |
Petiole length (cm) | 1.0 | 0.24 | 33 | 1.62 | 0.43 | 33 | 1.61 | 0.51 | 33 |
Leaf blade aspect ratio | 3.27 | 0.73 | 33 | 2.83 | 0.33 | 33 | 3.02 | 0.43 | 33 |
Morphological comparison of Q. sontraensis and its related species A box plot of leaf blade length B box plot of leaf blade width C box plot of petiole length D box plot of leaf blade aspect ratio. Red dots in the box plots indicate the mean value. Significant differences level (p) resulted from a Games-Howell post-hoc test (Comparison shown: only significant).
The Maximum Likelihood tree, based on MIG-seq data for 15 samples of Quercus, strongly supports two major clades (except outgroup: Lithocarpus vuquangensis, L. vinhensis and L. dahuoaiensis) consisting of clade 1 and clade 2, with 100% bootstrap value (Fig.
The morphological examination and the MIG-seq tree support Quercus sontraensis as being closely related to Q. langbiangensis and Q. cambodiensis. Morphological differentiation of leaf characters is moderate and mainly shown through statistical measures (Fig.
Quercus sontraensis is morphologically similar to Q. cambodiensis and Q. langbianensis in leaf shape (lanceolate to elliptic), cupules with 6–9 rings and cupule enclosing less than ½ of the nut. However, Q. sontraensis is distinguished from Q. cambodiensis by its leaf margin regularly and distinctly serrate on the upper 1/3–1/4 (–1/5) of the lamina (vs. almost entire or with a few low teeth in upper 1/4), bowl-shaped cupule (vs. cup-shaped), cupule bract margin distinctly toothed in all rings, except two upper rings (vs. entire, except distinctly toothed in two lower rings) and differs from Q. langbianensis in having bowl-shaped cupule (vs. cup-shaped), cupule bract margin distinctly toothed in all rings, except two upper rings (vs. distinctly toothed in all rings), broadly ellipsoid nut (vs. obovoid to ellipsoid) and slightly convex nut scar (vs. convex).
Vietnam. Da Nang City, Son Tra Peninsula, Son Tra Nature Reserve, in evergreen forest, alt. 340 m, 16°08'22.90"N, 108°15'28.85"E, 9 October 2016, Son H.T., Binh H.T., Ngoc N.V. QC201 (holotype DLU!, isotypes HN!, VNM!, VAFS!).
Tree, 12 m tall. Terminal and lateral buds ovoid, 3–5 mm long, 1.5–3 mm in diam., scales in 3–5 rows, imbricate, ovate-triangular, ca. 1.5 × 2 mm, apex obtuse, margin yellowish-brown ciliate, appressed hairy on both surfaces. Young twigs greyish-brown, 1.5–2 mm in diam., densely curly golden hairy, sometimes sulcate, old twigs greyish-brown, glabrous, lenticellate. Leaves alternate; blades elliptic to elliptic-lanceolate, 7–12.5 × 2.2–3.5 cm, acuminate or sometimes acute at apex, cuneate at base, margin regularly and distinctly serrate in the upper 1/3–1/4 (–1/5), densely golden hair on both surfaces when young, glabrescent, midrib sunken adaxially, prominent abaxially, lateral veins (8–)11–14 pairs, straight and running into the teeth of margin, slightly sunken adaxially, prominent abaxially, at an angle of 45–50(–52) degrees from midrib, tertiary veins scalariform, faint on the upper surfaces and conspicuous on the lower surfaces; petioles (0.7–)1–1.5 cm long, densely curly golden hairy when young, soon glabrous. Male inflorescence 7–9 cm long. Female inflorescence 2.5–3.5 cm long, female flowers solitary. Infructescences axillary or terminal, erect, rachis 0.5–0.8 (–1.2) cm long, 3–4 (–6) mm in diam., densely golden hairy. Fruits 1–3, 3–3.3 cm long (including cupule), sessile; cupules bowl-shaped, 1.2–1.7 (–1.9) cm long, 1.3–2.2 cm in diam., enclosing 1/3 of the nut when mature, both outside and inside covered with densely appressed yellowish-brown hairs, wall ca. 1.5–3 mm thick, comprising scales, scales arranged in 7–8 rings, margin of the ring distinctly toothed in all rings, except two upper rings; nut broadly ellipsoid 2.3–2.6 cm long, 1.7–2.0 cm in diam., densely golden hairy, apex nearly flat, densely appressed curly golden hairs around stylopodia, stylopodia up to 1.5 mm long, basal scar 1.1–1.3 cm in diam., slightly convex, glabrous.
Vietnam. Da Nang City, Son Tra Nature Reserve.
The specific epithet is derived from the district name of the type locality, Son Tra Nature Reserve, Son Tra Peninsula, Da Nang City, Central Vietnam.
Sồi Sơn Trà (suggested here).
Flowering from January to March, fruiting specimens were collected from September to October.
Vietnam. Da Nang City, Son Tra Peninsula, Son Tra Nature Reserve, in evergreen forest, 385 m elev., 16°07'41.7"N, 108°15'55.7"E, 20 September 2019, Son H.T. QC202 [fr.] (DLU!, VAFS!); ibid., 428 m elev., 16°07'00.3"N, 108°17'40.5"E, 20 September 2019, Son H.T. QC203 [fl.] (DLU!, VAFS!).
During our floristic survey inside the protected area of Son Tra Nature Reserve, less than 10 mature individuals of Quercus sontraensis were found in the evergreen forest, from 340 to 430 m altitude. According to the criteria established by the IUCN Red List (
We wish to thank the curators and staff of the following Herbaria DLU, FU, K, P and VNM for making their materials accessible. Additionally, our thanks to the Reviewers and Editors of the Journal for their valuable comments which helped us to improve the quality of the manuscript. This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 106.03-2019.19.