Smilax bolavenensis, a new species of Smilacaceae from southern Laos

Abstract

A new species of Smilax, S. bolavenensis (Smilacaceae), is described from the Bolaven Plateau, southern Laos. It is similar to S. elegantissima in its elongated inflorescence with slightly zigzagged rachis longer than 20 cm, but the new species is distinguished by its terete stem and petiole (vs. 4-angled with each corner narrowly winged in S. elegantissima) and 42–54-flowered umbels (vs. 7–12). A description, photographs and preliminary conservation status are also provided for S. bolavenensis.

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Phytotaxa 585 (1): 055–060
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Copyright © 2023 Magnolia Press Article PHYTOTAXA
ISSN 1179-3155 (print edition)
ISSN 1179-3163 (online edition)
Accepted by Mark W. Chase: 3 Feb. 2023; published: 23 Feb. 2023
https://doi.org/10.11646/phytotaxa.585.1.6
55
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Smilax bolavenensis, a new species of Smilacaceae from southern Laos
SHUICHIRO TAGANE1,4,*, PHETLASY SOULADETH2,5 & MINORU N. TAMURA3,6
1Kagoshima University Museum, Kagoshima University, 1-21-30, Korimoto, Kagoshima 890-0065, Japan
2Faculty of Forest Science, National University of Laos, Dongdok Campus, Xaythany District, Vientiane Capital, Laos
3Department of Botany, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
4
�
stagane29@gmail.com; https://orcid.org/0000-0002-1974-7329
5
�
p.souladeth@nuol.edu.la; https://orcid.org/0000-0001-8563-1773
6
�
mntamura@sys.bot.kyoto-u.ac.jp; https://orcid.org/0000-0002-5774-3353
*Corresponding author
Abstract
A new species of Smilax, S. bolavenensis (Smilacaceae), is described from the Bolaven Plateau, southern Laos. It is similar
to S. elegantissima in its elongated inflorescence with slightly zigzagged rachis longer than 20 cm, but the new species
is distinguished by its terete stem and petiole (vs. 4-angled with each corner narrowly winged in S. elegantissima) and
42–54-flowered umbels (vs. 7–12). A description, photographs and preliminary conservation status are also provided for S.
bolavenensis.
Keywords: Bolaven Plateau, Liliales, Southeast Asian flora
Introduction
Smilax Linnaeus (1753: 1028) became the sole genus of Smilacaceae after Heterosmilax Kunth (1850: 270) was
reduced to Smilax (Cameron & Fu 2006, Qi et al. 2013a, b). It consists of about 300 species, collectively distributed
in tropical, subtropical and temperate regions (Chen & Koyama 2000, POWO 2022). The species are dioecious, often
woody climbers and shrubs, sometimes herbs, with simple lamina with 3–7 main veins arising from the base, netted
leaf venation, axillary inflorescences are composed of 1(–3) umbel(s) or paniculately, racemosely or spicately disposed
several umbels, 6 tepals, superior ovary and drupes or berries (Chen & Koyama 2000, Qi et al. 2013a). In Laos, 19
species have been recorded (Gagnepain 1934, Koyama 1983, Newman et al. 2017 onwards, Kladwong et al. 2018,
2022).
The Bolaven Plateau, southern Laos, is one of the biodiversity hotspots in Indochina (Profile 2012). Indeed,
our recent extensive fieldwork carried out in the area 2018–2020 has resulted in discovery of more than 17 new
taxa endemic to the Bolaven Plateau and 70 new records for Laos (e.g., Souladeth et al. 2020, Tagane et al. 2020,
Phonepaseuth et al. 2021, Souvannakhoummane et al. 2021, Vongthavone et al. 2021, Yamazaki et al. 2021, Noyori
et al. 2022). During our botanical inventories, we collected seven species of Smilax, of which six were identified as S.
bockii Warburg ex Diels (1900: 252), S. corbularia Kunth (1850: 262), S. extensa Wallich in Hooker (1892: 309), S.
glabra Roxburgh (1832: 792), S. lanceifolia Roxburgh (1832: 792) and S. megacarpa Candolle (1878: 186). However,
one species did not match descriptions of species recorded in Laos and surrounding countries.
The two unknown specimens were collected during our field surveys in Bolaven Plateau in 2018 and 2019. We
examined the putative new species and referred to herbarium specimens at FOF and KAG and digital specimen images
available on online (e.g. JSTOR Global Plants https://plants.jstor.org). Floral measurements were made on rehydrated
specimens, and we consulted the relevant literature (Gagnepain 1934a, Koyama 1975, 1983, Hô 2000, Li et al. 2011,
Heckroth et al. 2014, Sun et al. 2015, Jin et al. 2016, Qi et al. 2016, Newman et al. 2017 onwards, Baruah et al. 2018,
Kladwong et al. 2018, 2020, Feng et al. 2022). Based on these studies, it was clear this is an undescribed species,
which we formally described below.

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Taxonomy
Smilax bolavenensis Tagane & Soulad., sp. nov. (Figs 1, 2)
TYPE:—LAOS. Champasak Province: Paksong District, near Nong Luang Village, Dong Hua Sao National Park (Bolaven Plateau),
15°04′44.53″N, 106°12′27.36″E, 1249 m a.s.l., 17 Dec 2019, Souladeth et al. L3342 (holotype: FOF 0006673; isotypes BKF, KAG
155707).
Smilax bolavenensis is similar to S. elegantissima Gagnepain (1934b: 619) from Vietnam in having an elongate inflorescence with slightly
zigzag rachis longer than 20 cm, but clearly distinguished from it by its terete stem and petiole (vs. 4-angled with each corner
narrowly winged) and 42–54-flowered umbels (vs. 7–12).
FIGURE 1. Smilax bolavenensis (holotype, Souladeth et al. L3342, FOF0006673).

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FIGURE 2. Smilax bolavenensis. A. Leafy branch. B. Branch with staminate inflorescence. C. Abaxial leaf surface. D., E. Staminate
inflorescence. F. Longitudinal section of a staminate umbel. G. Bracteole. H. Staminate flower bud with bracteoles (left), staminate flower
bud (middle), and staminate flower bud outer three tepals and one inner tepal removed showing stamens (right). I. Outer tepals (top) and
inner tepals (bottom), adaxial side (left), abaxial side (middle and right). A–C from Tagane et al. L1964 (KAG); D–G from Souladeth et
al. L3342 (KAG). Scale bars: F = 5 mm, G–I= 2 mm. Photographed by S. Tagane.
Climbers to 4 m tall, all parts glabrous. Stems and branches subterete, without prickles and wings. Petioles 3.5–4.5 cm
long, subterete; sheaths 1.2–1.7 × 0.7–1 cm. Tendrils up to 10.0 cm long, 1.0–1.5 cm above from the base of sheath.
Lamina ovate-oblong to narrowly ovate, (11.0–)15.2–22.4 × (3.5–)5.8–13.6 cm, shiny brownish red to brownish
yellowish on both surfaces when dry or paler and glaucous abaxially, apex acuminate, acumen up to 0.6 cm long, base
cordate, 5-veined, major veins diverging at base of lamina, prominent abaxially, (0.9–)1.7–2.5 cm interval (at widest
point of lamina), connected with reticulate veinlets. Staminate inflorescence composed of spicately disposed umbels,
to 33 cm long, 2–4-branched, rachis slightly zigzagged, not winged; umbels sessile, 22 per inflorescence, 42–54-
flowered, prophylls ovate-lanceolate, 3.0–4.5 × 1.0–1.2 mm, apex acuminate; receptacle of an umbel globose, 2.8 mm

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in diam.; bracteoles 4–5, ovate-triangular to oblong-obovate, 1.6–2.5 × 0.6–1.2 mm, apex acute. Staminate flower
(before anthesis), tepals 6, free from base, outer ones ovate-oblong, 2.5–2.9 × 1.3–1.5 mm, inner ones narrowly ovate,
2.0–2.2 × 0.9–1.0 mm long, apex acute, stamens 6, filaments sessile, anthers oblong, 1.3 mm long; pedicels 0.3–0.7
mm long. Pistillate inflorescence, fruits and seeds not seen.
Distribution:—Thus far known only from the Bolaven Plateau.
Habitat:—Montane forests, 1240–1250 m a.s.l., dominated by Fagaceae, Lauraceae and Myrtaceae, along with
some subcanopy trees such as Taberaemontana bovina (Apocynaceae), Aporosa yunnanensis (Phyllanthaceae), and
Camellia bolavenensis (Theaceae).
Phenology:—Staminate inflorescence with flower buds collected in December.
Etymology:—Referring to the type locality, Bolaven Plateau.
Vernacular name:—Kheau kheaung Bolaven ( ; Lao), suggested here. Kheau kheaung in
Lao refers to a common name for Smilax.
Preliminary conservation assessment:—Critically endangered (CR). During our five intensive field surveys in
Bolaven Plateau 2018–2020, we found only one population with a few individuals in lower montane forest on the top
of a plateau where we collected the above two specimens. Therefore, the most appropriate initial assessment of the
IUCN conservation status for this species is critically endangered (CR) under criteria D (IUCN 2012). In the Bolaven
Plateau, the forests at higher elevation have been decreasing due to dam construction and coffee plantations, which
may produce negative effects for S. bolavenensis. Further information on its distribution and number of individuals/
populations is needed to accurately assess its status and conserve this species.
Note:—Among the Smilax species in Laos, S. bolavenensis resembles S. glabra in leaf texture and venation
patterns, and both species occur in Bolaven Plateau (specimens of S. glabra: Souladeth et al. L3754, FOF, KAG).
However, S. bolavenensis is easily distinguishable from S. glabra by its long-spicately disposed sessile umbels (vs.
only 1 umbel axillary in S. glabra) and its cordate leaf base (vs. cuneate to rounded).
Additional specimen examined:—LAOS. Champasak Province: Paksong District, near Nong Luang Village,
Dong Hua Sao National Park (Bolaven Plateau), 15°04′19.26″N, 106°12′38.67″E, 1248 m a.s.l., 10 Dec 2018, Tagane
et al. L1964 (FOF 005293, FU, KAG 128065).
Acknowledgments
Authors thank the manager and staff of Dong Hua Sao National Park for permitting our botanical inventories in
the protected area. This study was supported by Nagao Natural Environment Foundation, Japan and partly by JSPS
KAKENHI (21K06307 and 21KK0132).
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