Eriolaena bacgiangensis (Malvaceae), a new species from Vietnam

Van Tien Tran; The Bach Tran; Ha Phuong Vu; Hoang Tuan Cao; Thu Ha Bui

doi:10.3897/phytokeys.256.152884

Research Article

Eriolaena bacgiangensis (Malvaceae), a new species from Vietnam

Van Tien Tran^‡, The Bach Tran^§|, Ha Phuong Vu^|, Hoang Tuan Cao^¶, Thu Ha Bui^¶

‡ Academy of Public Administration and Governance, Hanoi, Vietnam

§ Graduate University of Science and Technology, Ha Noi, Vietnam

| Vietnam Academy of Science and Technology, Ha Noi, Vietnam

¶ Hanoi National University of Education, Ha Noi, Vietnam

Corresponding author: Thu Ha Bui ( thuhabui.plant@gmail.com )

Academic editor: Matheus Colli-Silva

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: Tran VT, Tran TB, Vu HP, Cao HT, Bui TH (2025) Eriolaena bacgiangensis (Malvaceae), a new species from Vietnam. PhytoKeys 256: 13-20. https://doi.org/10.3897/phytokeys.256.152884

Abstract

The new species Eriolaena bacgiangensis from Vietnam is described and illustrated. The identified key was constructed to indicate the differences amongst three allied species of Eriolaena. E. bacgiangensis was compared with similar species, E. candollei and E. wallichii. E. bacgiangensis differs from E. candollei by the length of pedicel (1.4–2.3 cm long vs. 3.0–4.0 cm in E. candollei); presence of epicalyx after flowers at anthesis in E. bacgiangensis (vs. absence of epicalyx after flowers at anthesis in E. candollei); densely fringed epicalyx in E. bacgiangensis (vs. sparsely fringed epicalyx in E. candollei); style significantly exceeds staminal tube length in E. bacgiangensis, while the style is slightly longer than the staminal tube in E. candollei; the fruit apex round in E. bacgiangensis (vs. pointed and beaked in E. candollei). The linear epicalyx lobes are a key diagnostic trait for distinguishing E. bacgiangensis from E. wallichii (linear vs. ovate in E. wallichii). In addition, the other different characteristics of the two species are: leaf blade (not thickly papery in E. bacgiangensis vs. thickly papery in E. wallichii); length of inflorescences (13.0–18.0 cm in E. bacgiangensis vs. ≤ 6.0 cm in E. wallichii); shape of flower bud (lanceolate in E. bacgiangensis vs. globular in E. wallichii); fruit apex (round in E. bacgiangensis vs. apex shortly beaked in E. wallichii).

Key words:

Bac Giang, Dombeyoideae, Eriolaena, Vietnam

Introduction

Eriolaena DC. was established in 1823. This genus is now recognised as a genus in the subfamily Dombeyoideae, family Malvaceae (Colli-Silva et al. 2025). The genus comprises approximately 17 species (Ya et al. 2007), mainly distributed in tropical and subtropical Asia. In Vietnam, one species of Eriolaena (E. candollei) has been recorded so far (Gagnepain 1910; Nguyen et al. 1980; Pham 1999; Chamlong 2001; Nguyen 2003; Newman et al. 2007; Ya et al. 2007; Chandramohan et al. 2020; POWO 2025). E. candollei includes three synonyms such as E. affinis Pierre, E. glabrescens DC. and E. kwangsiensis Hand.-Mazz. (POWO 2025). The species is native to Bangladesh, Cambodia, south-central China, southeast China, East Himalaya, India, Laos, Myanmar, Thailand and Vietnam (POWO 2025). In 2025, during a botanical survey of Bac Giang Province, Vietnam, specimens of the genus Eriolaena were collected from this Province. After comparing with specimens in the Herbaria HN, K, KRIB, P and VNM and consulting the relevant literature, we determined that our specimens represent a new species. Here, we describe and illustrate this new species as Eriolaena bacgiangensis T.H.Bui.

Materials and methods

All morphological characters of the new species were observed from living and dried specimens. Material was stored at HN Herbarium of the Institute of Biology in Vietnam. The conservation status of the new species was assessed according to the guidelines of the International Union for Conservation of Nature (IUCN 2025). Other specimens of Eriolaena species are studied at HN, KRIB, VNM Herbaria that preserve many specimens of species distributed in Vietnam (acronyms follow Thiers (2025)).

Taxonomy

Eriolaena bacgiangensis T.H.Bui, sp. nov.

urn:lsid:ipni.org:names:77360921-1

Figs 1, 2, 3

Type.

Vietnam. • Bac Giang Province, Son Dong District, Huu San Commune, 21°23'26.1"N, 106°57'27.6"E, alt. 178 m, 18 July 2015, T.B. Tran, D.B. Tran, T.C. Vu, V.H. Do, H.Q. Bui, H.S. Doan, VK 6489 (holotype: HN80497!; isotypes: HN80498!, HN80499!, HN80500!, VNM00074095!).

Diagnosis.

Eriolaena bacgiangensis is most similar to E. candollei due to the shape of the leaf blade, number of basal and lateral veins, presence of epicalyx in the flower bud, lanceolate epicalyx; shape of sepal (linear–lanceolate) and yellow petals. E. bacgiangensis differs from E. candollei by the pedicel length (1.4–2.3 cm), presence of epicalyx after flowers at anthesis, densely fringed epicalyx, style significantly exceeds staminal tube length and fruit apex round.

Description.

Small tree up to 8 m tall; branchlets stellate puberulent. Stipules caducous. Petioles 1.1–6.0 cm long, densely pubescent. Leaf blades cordate, 7.0–23 × 3.6–18.0 cm; apex acute to caudate; base shallowly cordate; surfaces pubescent; veins densely pubescent; stellate hairy, denser abaxially; margin obtusely dentate; basal veins 5–7; secondary veins 3–5-paired. Inflorescence racemose, axillary to terminal, 3–10-flowered, 13.0–18.0 cm long. Flower pedicels 1.4–2.3 cm long, densely pubescent. Flower buds with epicalyx; epicalyx horizontal or pendulous; lanceolate, 1.5–1.6 × 0.6–0.7 cm, densely pubescent. Epicalyx present after flowers at anthesis, 1.3–1.5 × 0.2–0.4 cm; epicalyx lobe linear, margin pinnately partite, densely fringed, densely woolly stellate pilose. Calyx and corolla 5-merous. Sepals 5, valvate, linear–lanceolate, 2.0–2.9 × 0.47–0.53 cm; abaxially stellate hairy, adaxially villous. Petals 5, yellow to orange, oblong-rectangle; petals are turned backwards between the sepals; 1.3–1.5 × 0.6–0.7 cm, broader than sepals; above part glabrous; apex entire to emarginate; narrowed towards the base, claw broad, thick densely pubescent, deflexed between the sepals. Stamens many, connate into cylindrical tube; staminal tube covering the ovary and style, 1.1–1.3 cm long; anthers linear-oblong to rectangular, 0.21–0.31 × 0.04 cm, 2-celled, cells parallel. Ovary superior, ovate, 0.07–0.08 × 0.05–0.06 cm, pubescent; style linear, simple, 2.0–2.2 cm long, style significantly exceeds staminal tube length; stigma 5–7-lobed, lobes needle-like, horizontal to down-curved. Capsules ovate-elliptic, woody, 2.0–2.5 × 1.3–1.8 cm, longitudinally grooved, fruit apex round; fruit stalk 3.5–3.7 cm long; densely hairy.

Figure 1.

Eriolaena bacgiangensis T.H.Bui A habit B flowering, fruiting branch C leaves D cordate base E dentate margin F flower bud and flower G epicalyx lobes H–J flower K flower from below L staminal tube, style, stigma M, N fruit (Photos by T.B. Tran).

Etymology.

The specific epithet refers to the type locality, Bac Giang Province in Vietnam.

Distribution and ecology.

E. bacgiangensis is found only in Vietnam, Bac Giang Province, Son Dong District, Huu San Commune, where it grows in well-lit places in shrubland and dry soil of secondary forest, in association with Acacia mangium Willd., Bidens pilosa L., Cayratia trifolia (L.) Mabb. & J.Wen, Chromolaena odorata (L.) R.M.King & H.Rob. and Stachytarpheta jamaicensis (L.) Vahl. Flowering and fruiting specimens were collected in July 2015.

Figure 2.

Eriolaena bacgiangensis T.H.Bui A flowering, fruiting branch B pubescent branch C pubescent leave D–F stellate hairs on leaves G fruit (Drawn by Le Kim Chi).

Conservation status.

Data Deficient (DD) (IUCN 2025). Eriolaena bacgiangensis is known only from the type locality. A comprehensive botanical survey of the Eriolaena has not been carried out to date. Potential threats from habitat fragmentation for road construction and land-use change for Acacia spp. plantations, therefore, require urgent and appropriate plans for ex situ species conservation.

Figure 3.

Eriolaena bacgiangensis T.H.Bui A flower bud B, C bloom flower D epicalyx lobes E, G flower F flower from below H staminal tube, style, stigma I stamens J fruit (Drawn by Le Kim Chi).

Discussion

Diagnostic characters separating the allied species are listed in Table 1. Based on keys to species of Eriolaena mentioned in previous works (Ya et al. 2007; Chandramohan et al. 2020), we determined two species of Eriolaena (E. candollei, E. wallichii) with some similar features to the specimens we collected (branchlets stellate pubescent, stipules caducous, inflorescence axillary or terminal, pedicel with stellate hairy, flower bud with epicalyx, sepals 5, sepal linear–lanceolate, petals 5, fruit pubescent).

Table 1.

Download as

CSV

XLSX

Morphological comparison of E. bacgiangensis with similar species.

Characters	E. bacgiangensis	E. candollei	E. wallichii
Habit	small tree up to 8 m tall	tree up to 20 m tall	trees up to 6 m tall
Shape of flower bud	lanceolate	lanceolate	globular
Epicalyx (absent/present) after flowers at anthesis	present	absent	present
Margins of epicalyx lobes	deeply, densely fringed	sparsely fringed	deeply fimbriate
Comparison between style and staminal tube	style significantly exceeds staminal tube length	style slightly longer than staminal tube	–
Fruit apex	round	pointed and beaked	apex shortly beaked
Length of fruit stalk (cm)	3.5–3.7	1.0–3.0	ca. 1.5

Two easily recognisable features of the epicalyx which we used to distinguish E. bacgiangensis from E. candollei include the presence of the epicalyx after flowers at anthesis and densely fringed epicalyx in E. bacgiangensis (vs. absence of epicalyx after flowers at anthesis and sparsely fringed epicalyx in E. candollei).

The shape of the epicalyx lobe can be used to distinguish E. bacgiangensis from E. wallichii (linear vs. ovate in E. wallichii). Therefore, the characteristics of the epicalyx are very important for the identification of E. bacgiangensis. In addition, the other differences in characteristics of the two species are: leaf blade (not thickly papery in E. bacgiangensis vs. thickly papery in E. wallichii); length of inflorescences (13.0–18.0 cm in E. bacgiangensis vs. ≤ 6.0 cm in E. wallichii); shape of flower bud (lanceolate in E. bacgiangensis vs. globular in E. wallichii); fruit apex (round in E. bacgiangensis vs. apex shortly beaked in E. wallichii).

Key to three species E. bacgiangensis, E. candollei and E. wallichii

1	Inflorescences ≤ 6.0 cm long. Flower bud globular	*E. wallichii*
–	Inflorescences ≥ 7.0 cm long. Flower bud lanceolate	2
2	Pedicel 3.0–4.0 cm long. Epicalyx lobes sparsely fringed, epicalyx absent after anthesis. Width of ovary 0.2–0.3 cm long, style slightly longer than staminal tube. Apex of fruit pointed and beaked, fruit stalk 1.0–3.0 cm long	*E. candollei*
–	Pedicel 1.4–2.3 cm long. Epicalyx lobes densely fringed, epicalyx present after anthesis. Width of ovary 0.5–0.6 cm long, style much longer than the staminal tube. Apex of fruit round, fruit stalk 3.5–3.7 cm long	*E. bacgiangensis*

Additional specimens examined

E. candollei: VIETNAM. Lang Son: Lang Met, 4/7/1944, Petelot, Petelot 6899 (VNM); Ninh Binh: Cuc Phuong, N.M Cuong, NMC 139 (HN); Thanh Hoa, 1921, Poilane, Poilane 1611 (VNM); Kon Tum: Sa Thay, Sa Son, 4/5/2009, T.T. Bach, V.T Chinh, D.V. Hai, B.H. Quang, VK 2630 (HN, KRIB); Dak Lak: Buon Ma Thuot, 17/1/1956, Pierre, Pierre 133 (VNM). LAOS: Xiangkhouang, 6/4/1949, Vidal, s.n. (VNM).

Acknowledgements

We thank the directors and curators of the Herbaria HN, K, KRIB, P and VNM for allowing access to and/or for providing high quality images of herbarium specimens. Le Kim Chi for preparing the drawing.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Funding

Funding for this research was provided by the project ĐTĐL.CN-72/22.

Author contributions

Van Tien Tran: Identification, description, key establishing and manuscript writing. Ha Phuong Vu, Hoang Tuan Cao: Study on specimens at VNM herbarium and related references. The Bach Tran: Investigation, study on specimens at HN and KRIB Herbaria. Thu Ha Bui: description, key establishing and manuscript correction.

Author ORCIDs

Van Tien Tran https://orcid.org/0000-0001-7407-318X

The Bach Tran https://orcid.org/0000-0003-3798-5969

Ha Phuong Vu https://orcid.org/0009-0009-5765-5343

Hoang Tuan Cao https://orcid.org/0009-0002-3487-8295

Thu Ha Bui https://orcid.org/0000-0001-6971-0105

Data availability

All of the data that support the findings of this study are available in the main text.

References

Chamlong P (2001) Sterculiaceae. Flora of Thailand. The Forest Herbarium, Royal Forest Department, Bangkok 7: 351–654.

Chandramohan K, Mahesh Y, Rambabu K, Kiran E (2020) A taxonomic revision of the genus Eriolaena (Malvaceae) in India. Annals of Plant Sciences 9(1): 3681–3692.

Colli-Silva Pérez-Escobar OA, Ferreira CDM, Costa MTR, Gerace S, Coutinho TS, Yoshikawa VN, Antonio-Domingues H, Hernández-Gutiérrez R, Bovini MG, Duarte MC, Cheek M, Chase MW, Fay MF, Christenhusz MJM, Dorr LJ, Schoeplein C, Corcoran M, Roy S, Cable S, McLay T, Maurin O, Forest F, Baker WJ, Antonelli A (2025) Taxonomy in the light of incongruence: An updated classificationof Malvales and Malvaceae based on phylogenomic data. Taxon 74(2): 361–385. https://doi.org/10.1002/tax.13300

Gagnepain F (1910) Sterculiacées. In: Lecomte PH (Ed.) Flore Générale de l’Indo-Chine. Masson & Co. , Paris, 1: 454–481.

IUCN (2025) The IUCN Red List of Threatened Species. Version 2025-1. https://www.iucnredlist.org [Accessed on 19 April 2025]

Newman M, Ketphanh S, Svengsuksa B, Thomas P, Sendala K, Lamxay V, Amstrong K (2007) A checklist of the vascular plants of Lao PDR. Royal Botanic Garden Edinburgh.

Nguyen TB (2003) Sterculiaceae. In: Nguyen TB (Ed.) A Checklist of plant species in Vietnam. Agricultural Publishing House 2: 548–552.

Nguyen BQ, Vu VD, Nguyen NC, Cao TC (1980) Vietnam Forest Trees. Agricultural Publishing House 3: 152–153.

Pham HH (1999) Sterculiaceae. An illustrated flora of Vietnam. Youth Publishing House, Ho Chi Minh City, 1: 491–513.

POWO (2025) Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet. http://www.plantsoftheworldonline.org/ [Retrieved 09 February 2023]

Thiers B (2025) Index Herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. http://sweetgum.nybg.org/ sci-ence/ [Retrieved 26 February 2025]

Ya T, Michael GG, Laurence JD (2007) Flora of China. Science Press, Beijing/Missouri Botanical Garden Press, 12: 303–310.

﻿Abstract