Loropetalum flavum (Hamamelidaceae), a new species from northern Vietnam

Abstract

Loropetalum flavum (Hamamelidaceae) is described and illustrated as a new species from Bat Dai Son Mountains situated in the northern Vietnam. Recently discovered plant was observed as a typical element of the rich primary forest found on the highly eroded karstic limestone mountain formations allied to the border with China. The new species is characterized by arboreous habit; stellately indumentum of branchlets, leaves and flowers; axillary, capitate, 4–12-flowered inflorescences; yellow, sessile, actinomorphic, bisexual, 4–6-merous flowers with 2-whorled perianth and 2–8 fleshy disc lobes; stamens with conspicuous subulate connective protrusion; anthers with 2 rectangular 2-sporangiate thecae, each dehiscing by 2 valves and syncarpous gynoecium with 2-locular inferior ovary bearing 2 very short separate styles. A key to all known species of Loropetalum species is given and lectotype of L. lanceum is proposed.

Full text

Phytotaxa 385 (2): 094–100
http://www.mapress.com/j/pt/
Copyright © 2018 Magnolia Press Article PHYTOTAXA
ISSN 1179-3155 (print edition)
ISSN 1179-3163 (online edition)
94 Accepted by Jens Rohwer: 14 Dec. 2018; published: 28 Dec. 2018
https://doi.org/10.11646/phytotaxa.385.2.5
Loropetalum flavum (Hamamelidaceae), a new species from northern Vietnam
LEONID V. AVERYANOV1, PETER K. ENDRESS2, KHANG SINH NGUYEN3, TRAN HUY THAI3, TATIANA V.
MAISAK1, ANNA L. AVERYANOVA1 & LE NGOC DIEP3
1 Komarov Botanical Institute, Russian Academy of Science, St. Petersburg, Prof. Popov Str. 2, Russia, 197376.
2 Department of Systematic and Evolutionary Botany, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland.
3 Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi,
Vietnam.
* Author for correspondence; E-mail: av_leonid@mail.ru
Abstract
Loropetalum flavum (Hamamelidaceae) is described and illustrated as a new species from Bat Dai Son Mountains, northern
Vietnam. A key to all known species of Loropetalum is given and a lectotype of L. subcordatum is proposed.
Keywords: flora of Vietnam, limestone endemism, plant diversity, plant taxonomy
Introduction
Loropetalum R. Brown ex Reichenbach (1829: 87) is a small genus of Hamamelidaceae closely allied to the widespread
genus Hamamelis Linnaeus (1753: 124), species of which are widely known in horticulture. For a long time it included
three presently accepted species distributed in northeastern India, southern China and Japan (Feng at al. 1999, Zhang
et al. 2003). One more species of the genus morphologically allied to L. lanceum Handel-Mazzetti (1932: 123) and L.
chinense (R. Br. in Abel 1818: 375) Oliver (1862: 459) was recently discovered in the Bat Dai Son Mountains during
a plant diversity assessment of the Bat Dai Son Nature Reserve in northern Vietnam (Ha Giang province, Quan Ba
district). The plant is a typical element of the rich primary limestone forests found on karstic highly eroded remnant
mountain formations broadly distributed in northern Vietnam adjacent to the Chinese border. Along with the recently
discovered Disanthus ovatifolius Aver., P.K. Endress, B.H. Quang & K.S. Nguyen (Averyanov et al. 2017: 105) the
new species represents a significant new addition to the hamamelidaceous flora of Vietnam.
A formal description of the new species is provided below along with illustrations and data on its distribution,
phenology and ecology, as well as a key for identification of all known species of the genus.
Material and Methods
Specimens of the new species were collected in spring 2017. Fresh branches, inflorescences and flowers from living
plants were fixed and stored in 70% ethanol. Measurements of the floral parts for the description were made on both
herbarium and liquid-fixed material. Photos of flowers parts preserved in alcohol were taken with a digital monocular
microscope EDGDM003B10-HD16M (Shanghai Lingtech Technology Co.) with microscope camera ZX-200HD 1/3”
HDMI (Shenzhen Zhongxun Optics Instrument Co.). Standard versions of “Photoshop” and “Helicon focus” were
used for image processing. The online version of the IUCN Red List of Threatened Species (2018) was followed for
estimation of preliminary species conservation status.

SPECIES OF LOROPETALUM FLAVUM (HAMAMELIDACEAE) Phytotaxa 385 (2) © 2018 Magnolia Press • 95
Taxonomic Treatment
Loropetalum R. Brown ex Reichenbach 1829: 87.
Type:—L. chinense (R. Brown) Oliver 1862: 459.
≡ Hamamelis chinensis R. Brown 1818: 375.
4 species. NE. India, S. China, N. Vietnam, S. Japan.
Key for species identification
1. Branchlets almost glabrous; at least some leaves in apical half sparsely irregularly dentate; petioles 10–15 mm long; leaf blade at
the base rounded or subcordate; sterile bracts of peduncle pectinate, glandular fimbriate; inflorescence 14–25-flowered; sepals 1.5
mm long; petals bidentate at apex; styles about 2 mm long; plant growing 100–200 m a.s.l .................................1. L. subcordatum
–. Branchlets stellately pubescent; all leaves with entire margin; petioles 1.5–6 mm long; leaf blade at the base acute or cuneate;
sterile bracts of peduncle entire, without glandular hairs; inflorescence 4–16-flowered; sepals 1.8–3 mm long; petals entire at apex;
styles less than 0.5 mm long; plant growing 1000–1250 m a.s.l .......................................................................................................2.
2. Leaves almost glabrous; inflorescence with 4–5 flowers; flowers 4-merous, white .....................................................2. L. lanceum
–. Leaves stellately pubescent; inflorescence with 4–16 flowers; flowers 4–6-merous, white, yellow or red .....................................3.
3. Shrub 1–3 m tall; flowers pedicellate, white or red (rarely pale yellow); peduncle 8–10 mm long; stipules triangular-lanceolate to
obovate; leaf blade ovate, 2–6.5 cm long, acute to shortly acuminate, membranaceous, densely pubescent abaxially; inflorescence
terminal or axillary ........................................................................................................................................................ 3. L. chinense
–. Tree 5–10 m tall; flowers sessile, yellow; peduncle 2–7 mm long; stipules narrowly lanceolate; leaf blade lanceolate elliptic to
narrowly ovate, 5–12 cm long, attenuate, rigid, leathery, sparsely pubescent abaxially; inflorescence axillary ..............4. L. flavum
1. L. subcordatum (Bentham) Oliver 1883: 13–14, pl. 1417.
≡ Tetrathyrium subcordatum Bentham 1861: 133.
Lectotype (designated here):—CHINA. Hong Kong: Black Mountain, Charles Wilford s.n. (K000704907 photo!,
isolectotypes BM000906229 photo!, GH00043485 photo!).
Distribution:—SE. China (Guangdong, SW Guangxi, Guizhou, Hong Kong).
Habitat:—Secondary scrub at elevations 100–200 m a.s.l.
Note:—The best herbarium specimen among three available type sheets, which is also the only one undoubtedly
bearing Bentham’s handwriting, is proposed as lectotype.
2. L. lanceum Handel-Mazzetti 1932: 123–124.
Holotype:—CHINA. Guangxi: Nanning, Shiwandashan, in forest, 750 m, 21 Oct. 1928, Ching 8078 (W1940-0004802
photo!, isotypes: NAS00071164 photo!, IBSC0001056 photo!, NAS00345195 photo!, PE00029879 photo!).
Distribution:—SE. China (Guangxi, Guizhou).
Habitat:—Evergreen montane forests at elevations about 1000 m a.s.l.
Note:—Handel-Mazzetti (1932) did not indicate a holotype among his authentic specimens [“Prov. Kwangsi:
Nanning austr., Seh-feng-da-schan, in silva, copiose, 750 m., 21. X. 1928 (Ching 8078)”], but he worked in Vienna and
the specimen in W is the only one known bearing his handwriting.
3. L. chinense (R. Brown) Oliver 1862: 459.
≡ Hamamelis chinensis R. Brown in Abel 1818: 375.
Type:—CHINA. Jiangsu: near Nanjing [“China prope Nan-king”], Plukenet s.n. (type specimen location unknown).
Distribution:—NE. India, S. China (Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu,
Jiangxi, Sichuan, Yunnan, Zhejiang), S. Japan.
Habitat:—Mountain forests and secondary scrub at elevations 1000–1200 m a.s.l.
Note:—A search of databases of herbaria where Plukenet collections may be found or were mentioned (BM, L,
LE, OXF, JSTOR, etc.) did not give any positive results.
4. L. flavum Aver., P.K. Endress & K.S. Nguyen, sp. nov. (Fig. 1 & 2).
Diagnosis:—The new species differs from its closest relative L. chinense in arboreous habit, sessile yellow flowers, short peduncles 2–7
mm long, narrowly lanceolate stipules, always axillary inflorescences and large sparsely pubescent leathery leaves 5–12 cm long.

AVERYANOV ET AL.
96 • Phytotaxa 385 (2) © 2018 Magnolia Press
Type:—VIETNAM. Ha Giang province: Quan Ba district, Bat Dai Son commune, Pai Chu Phin village, Bat Dai Son Nature Reserve,
ca. 23º07ʹ54.9ʺN 104º59ʹ24.1ʺE, 1000–1220 m a.s.l., karstic highly eroded mountains composed of solid marble-like limestone,
not common, 16 April 2018, L. Averyanov, Nguyen Sinh Khang, Chuong Quang Ngan, T. Maisak, VR 265 (holotype LE01042163!,
isotypes HN0000073443!, HN0000073444!, LE01042164!, LE01042165!, LE01042166!).
FIGURE 1. Loropetalum flavum Aver., P.K. Endress & K.S. Nguyen. A—Flowering tree in natural habitat. B—Flowering branch. C–E—
Inflorescences. F—Flattened branch, adaxial view. G—Flattened branch, abaxial view. H—Petiole. I—Petiole indumentum. J—Leaves,
adaxial surface. K—Leaves, abaxial surface. L—Young branchlet. M—Scape. N—Flattened inflorescence, side view. O—Intact flowers,
frontal and half-side views. P—Intact flowers, side view. All photos were made from plant prior to preparation of the type herbarium
specimens (VR 265). Photos by L. Averyanov and Khang Sinh Nguyen, correction and plate design by L. Averyanov.

SPECIES OF LOROPETALUM FLAVUM (HAMAMELIDACEAE) Phytotaxa 385 (2) © 2018 Magnolia Press • 97
FIGURE 2. Loropetalum flavum Aver., P.K. Endress & K.S. Nguyen. A—Pressed inflorescence with half of the flowers removed.
B—Scape. C—Flattened flower, side view. D—Flattened flowers with apical part of petals removed, side view. E—Flattened flower with
frontal sepals removed, side view. F—Flattened flower with frontal sepals, petals and stamens removed, side view. G—Flattened 4, 5
and 6-merous flowers, view from below. H—Sepals, abaxial side. I—Sepals, adaxial side. J—Flower disc with frontal sepals, petals and
stamens removed, side view. K—Intact flower disc. L—Flower disc with disc lobes, frontal and oblique side views (petals and stamens
removed). M—Intact stamen, view from abaxial side. N—Stamens, side, abaxial and adaxial views at a different stage of thecae opening.
O—Upper part of ovary with styles, side view. P—Upper part of ovary with styles, view from above. Q—Ovary, sagittal section. R—
Median leaf vein on abaxial surface of lamina near its base. S—Leaf, abaxial surface. Photos were made from fresh material preserved in
alcohol, prior to preparation of type herbarium specimens (VR 265). All photos, correction and plate design by L. Averyanov.

AVERYANOV ET AL.
98 • Phytotaxa 385 (2) © 2018 Magnolia Press
Description:—Small evergreen hermaphrodite tree 5–10 m tall with diffuse irregular crown. Trunk and branches
dull brownish-gray to pale gray. Branches and leaves more or less densely hairy throughout, with light gray to almost
white stellate hairs. Young branches light gray-greenish, straight to slightly zigzag; young leaves dull pale pink-
brownish. Buds perulate, dull pale greenish, narrowly ovoid, obtuse, (2.5–)3–4(–4.5) mm long, consisting of (2–)3(–4)
rigid, coriaceous, concave, hairy bud scales, 2–3 mm long, 1.5–2 mm wide. Stipules relatively large, herbaceous,
narrowly lanceolate, acuminate, (3–)3.5–4.5(–5) mm long, (0.8–)1(–1.2) mm wide, rather flat, very early deciduous,
leaving small scars. Leaves alternate, indistinctly distichous, shortly petiolate; petiole rigid, subterete, dull green
to pale grey-green, (1.5–)2–4.5(–5) mm long, (1.2–)1.4–1.8(–2) mm in diameter, straight or slightly recurved; leaf
blade simple, leathery, rigid, broadly lanceolate elliptic to narrowly ovate, (5–)6–10(–12) cm long, (2.5–)3–4(–4.5)
cm wide, margin entire, base cuneate, apex acuminate, dark green above, pale light glaucous-green to whitish below;
venation pinnate, with 2 more or less prominent basal sub-opposite veins and 4–5(–6) pairs of lateral arcuate veins;
tertiary veins distinct on both surfaces (immersed adaxially, raised abaxially). Inflorescence axillary, pedunculate,
capitate, with (3–)4–10(–12) flowers. Scape bracteate, (2–)3–5(–7) mm long, densely hairy; sterile bracts (2–)3–5(–7)
spirally arranged, distant, minute, narrowly to broadly triangular, 0.3–0.5 mm long; rachis 0.4–0.8 mm long; floral
bracts absent. Flowers not widely opening, sessile, in a dense head-like cluster, densely adpressed to each other,
actinomorphic, bisexual, 4–6-merous, with 2-whorled perianth. Sepals 4–6, yellow, oblong ovate, (1.8–)2–2.4(–2.6)
mm long, (1–)1.2–1.4(–1.6) mm wide, recurved and often revolute at apex; glabrous adaxially, outside with dense to
sparse white stellate hairs. Petals 3–6(–7), linear-lorate to linear, yellow, glabrous, (9–)12–16(–18) mm long, (0.4–)
0.6–0.9(–1.1) mm broad, erect to spreading, straight to curved (circinate in bud) tapering to the base and apex, early
caducous, margins straight and entire. Androecium of (3–)4–6(–7) stamens; stamens free, glabrous, arranged in one
whorl; filaments slightly dorso-ventrally flattened, recurved to geniculate, (0.3–)0.4–0.6(–0.7) mm long, (0.25–)0.3–
0.4(–0.45) mm wide; anthers basifixed, (0.6–)0.7–0.8(–0.9) mm long, (0.5–)0.6–0.7(–0.8) mm wide, laterally with 2
rectangular 2-sporangiate thecae dehiscing by 2 valves; connective protrusion prominent, subulate, acuminate, as long
as anther or longer, (0.9–)1–1.1(–1.2) long, straight to recurved (occasionally connective protrusion elongate, petaloid).
Disc lobes (sometime called disc scales or staminodia) prominent, (2–)4–6(–8), in one whorl (inside staminal whorl),
alternate with stamens, fleshy, glabrous, oblate to hemispheric, flattened at apex, (0.3–)0.4–0.5(–0.6) mm in diameter.
Gynoecium syncarpous of 2 completely fused carpels; ovary inferior, obconoid, (1.2–)1.4–1.6(–1.8) mm long, (1.2–)
1.4–1.5(–1.6) mm wide, densely hairy, 2-locular, each locule with 1 ovule placed on basal placenta; floral disc almost
flat to slightly convex densely hairy with simple and stellate stiff white hairs; styles 2, purplish, separate, very short,
erect, cylindrical, straight to slightly recurved, (0.2–)0.25–0.3(–0.35) mm long, each with oblique-capitate, irregularly
brush-like coralloid stigma. Fruits and seeds unknown.
Etymology:—Species name refers to the yellow color of flowers.
Habitat, phenology and conservation status:—Small tree to 10 m tall. Primary evergreen broad-leaved and
coniferous humid forest with Pseudotsuga sinensis, Xanthocyparis vietnamensis and Pinus kwangtungensis on rocky
karstic limestone, at elevations 1000–1220 m a.s.l. Not common. Flowering in March–April. Estimated IUCN Red List
status DD.
Distribution:—N. Vietnam (Ha Giang province, Quan Ba district, Bat Dai Son nature reserve). Endemic of
northern Vietnam.
Notes:—The new species belongs to the subfamily Hamamelioideae, tribe Loropetaleae (Li & Bogle 2001)
in a group of three genera with stamens having 2-sporangiate thecae and a long horned connective protrusion (see
Endress 1989a, b; Hufford & Endress 1989). With its unusual brush-shaped stigma with multicellular branches it
fits with Loropetalum (Endress 1989a). Embolanthera differs by its winged petals and Maingaya by its long horned
staminodia. Loropetalum flavum is well segregated from presently known congeners (see Table 1). The new species is
morphologically more or less closely allied to the widespread L. chinense, from which it differs in arboreous life form
(vs. shrub 1–3 m tall), narrowly lanceolate stipules (vs. stipules triangular-lanceolate to obovate), lanceolate elliptic
to narrowly ovate, prominently acuminate, rigid, leathery leaves, 5–12 cm long (vs. ovate, acute to shortly acuminate,
membranaceous leaves, 2–6.5 cm long), axillary inflorescences (vs. inflorescences mostly terminal), peduncles 2–7
mm long (vs. peduncles 8–10 mm), sessile, 4–6-merous, yellow flowers (vs. flowers 4–5-merous, pedicellate, white
or red, rarely pale yellow). The new species is also somewhat similar to L. lanceum, from which it differs in stellately
pubescent leaves (vs. old leaves glabrescent), many-flowered inflorescences (vs. inflorescences with 4–5 flowers)
and 4–6-merous yellow flowers (vs. flowers white, 4-merous). Loropetalum flavum was observed as a typical tree on
karstic limestone hills very near to the Chinese border. Hence, the occurrence of this species may be expected in similar
habitats in adjacent southern China (southeastern Yunnan and southwestern Guangxi).

SPECIES OF LOROPETALUM FLAVUM (HAMAMELIDACEAE) Phytotaxa 385 (2) © 2018 Magnolia Press • 99
TABLE 1. Key morphological characters of Loropetalum species.
CHARACTER L. FLAVUM L. SUBCORDATUM L. LANCEUM L. CHINENSE
Life form Evergreen tree 5–10 m
tall
Evergreen shrub or tree
to 12 m tall
Evergreen tree 9–13
m tall
Evergreen or
semideciduous shrub
1–3 m tall
Branchlets hairiness Pubescent ±Early glabrescent Pubescent Pubescent
Stipule shape Narrowly lanceolate Lanceolate Lanceolate Triangular-lanceolate to
obovate
Petiole length (mm) 1.5–5 10–15 4–6 2–5
Leaf blade shape and
texture
Broadly lanceolate
elliptic to narrowly
ovate, rigid, leathery
Ovate or elliptic,
membranous or thinly
leathery
Lanceolate or broadly
lanceolate, membranous
or thinly leathery
Ovate, membranous
Leaf blade size (cm) 5–12 × 2.5–4.5 7–12 × 3.5–5 5–8.5 × 2.5–3.5 2–6.5 × 1–3
Leaf blade base Cuneate Rounded or subcordate Cuneate or obtuse Cuneate or rounded
Leaf blade apex Prominently acuminate Acute Caudate-acuminate Acute or shortly
acuminate
Leaf blade margin Entire Entire or sparsely
serrulate
Entire Entire
Number of lateral veins 4–6 pairs 6–8 pairs 4–6 pairs 4–8 pairs
Indumentum on abaxial
mature leaf surface
Sparsely stellately
pubescent
Almost glabrous Almost glabrous Densely stellately
pubescent
Inflorescence position Axillary Axillary Terminal Mostly terminal
Number of flowers in
inflorescence
4–12 14–25 4–5 4–16
Inflorescence shape Dense head Dense head Short spike Short raceme or head
Peduncle length (mm) 2–7 4–5 3–5 8–10
Peduncle scales Entire, without glandular
hairs
Pectinate, glandular
fimbriate
Entire, without
glandular hairs
Entire, without
glandular hairs
Character of flower 4–6-merous, sessile,
yellow
5–6-merous, sessile,
white
4-merous, sessile, white 4–5-merous, pedicelate,
white, pale yellow or
red
Sepal length (mm) 1.8–2.6 1.5 2–2.5 2–3
Petal length (mm) 9–18 15 10–13 10–20
Petal apex Entire, blunt or obtuse Bidentate Entire, blunt or obtuse Entire, blunt or obtuse
Disc lobes (2)4–6(8), hemispheric 5–10, teeth-like, oblong
ovate
? 4–9, scale-like
Flowering time March–April April–June March–May March–April
Elevation of habitat (m
a.s.l.)
1000–1250 100–200 1000 1200
Acknowledgements
Research work, the results of which are presented in this paper, was financially supported in part by the Vietnam
Academy of Science and Technology, international cooperation mission: QTRU01.07/18-19 and Russian Foundation
for Basic Research, 18-54-54005 Viet_a within the project “Assessment of the plant diversity in Bat Dai Son Mountains,
Ha Giang province” and was carried out in the framework of the institutional research project of the Komarov Botanical
Institute of the Russian Academy of Sciences “Study of the flora of Indochina” (АААА-А18-118031290070-6). The
authors cordially thank the Director of the Center for Plant Conservation, Hanoi (Vietnam Union of Science and
Technology Associations), Dr. Nguyen Tien Hiep for the fieldwork assistance.

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100 • Phytotaxa 385 (2) © 2018 Magnolia Press
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