Eriolaenabacgiangensis (Malvaceae), a new species from Vietnam

Abstract

Figures

Eriolaenabacgiangensis 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).

Eriolaenabacgiangensis 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).

Eriolaenabacgiangensis 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).

Tables

Table 1.. 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

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

Full text

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 Eriolaenabacgiangensis 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

Taxon classificationPlantae



T.H.Bui sp. nov.

B680676E-A003-5F1F-BA05-58D5CF7623EA

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.

Eriolaenabacgiangensis 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.

Eriolaenabacgiangensis 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 Acaciamangium Willd., Bidenspilosa L., Cayratiatrifolia (L.) Mabb. & J.Wen, Chromolaenaodorata (L.) R.M.King & H.Rob. and Stachytarphetajamaicensis (L.) Vahl. Flowering and fruiting specimens were collected in July 2015.

Eriolaenabacgiangensis 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). Eriolaenabacgiangensis 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.

Eriolaenabacgiangensis 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).

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

**: **

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).

Supplementary Material

XML Treatment for Eriolaena bacgiangensis