A new species of Sterculia (Malvaceae) from Vietnam

Cam Nhung Kieu; Duc Binh Tran; Ngoc Han Le; Thi Hoan Duong; Thu Ha Bui; Thu Thuy Nguyen; Hong Quang Bui; The Bach Tran

doi:10.3897/phytokeys.227.101754

Research Article

A new species of Sterculia (Malvaceae) from Vietnam

Cam Nhung Kieu^‡, Duc Binh Tran^‡§, Ngoc Han Le^§, Thi Hoan Duong^§, Thu Ha Bui^|, Thu Thuy Nguyen^§‡, Hong Quang Bui^‡§, The Bach Tran^‡§

‡ Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Ha Noi, Vietnam

§ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Ha Noi, Vietnam

| Hanoi National University of Education, Ha Noi, Vietnam

Corresponding author: The Bach Tran ( tranthebach.botany@gmail.com )

Academic editor: Duilio Iamonico

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: Kieu CN, Tran DB, Le NH, Duong TH, Bui TH, Nguyen TT, Bui HQ, Tran TB (2023) A new species of Sterculia (Malvaceae) from Vietnam. PhytoKeys 227: 1-8. https://doi.org/10.3897/phytokeys.227.101754

Abstract

A new species of Sterculia from Vietnam – S. konchurangensis – is described, illustrated, and compared with the similar S. lanceolata. S. konchurangensis differs from S. lanceolata by the length of the petiole (7.0–9.5 vs. 25–35 mm), shape of the leaf blade (obovate or elliptic vs. elliptic, lanceolate or elliptic-lanceolate), length of the leaf blade (6–8 vs. 9–20 cm), and length of the calyx lobe (11–12.5 vs. 4–6 mm). A diagnostic key of the 22 Sterculia species occurring in Vietnam is also provided.

Key words

Malvaceae, Sterculia, Tay Nguyen, Vietnam

Introduction

The genus Sterculia L. (Malvaceae Juss.) comprises 100–200 species mainly distributed in tropics and subtropics of both hemispheres, most abundant in Asian tropics (see e.g., Ya et al. 2007; POWO 2023; WFO 2023). The genus is characterized by having leaves simple, flowers unisexual, androgynophore present, staminodes at top of androgynophore in whorl around base of carpels (Ya et al. 2007). In Vietnam, 22 species of Sterculia have been recorded so far (Gagnepain 1910; Nguyen et al. 1980; Pham 1999; Chamlong 2001; Nguyen 2003; Newman et al. 2007; Ya et al. 2007; POWO 2023).

During a botanical survey of the Gia Lai province (the Central Highlands of Vietnam) in 2022, plants referred to the genus Sterculia were observed in a primary evergreen forest in the Kon Chu Rang Nature Reserve. After comparing the collected specimens with others preserved in various herbaria, and by consulting relevant literature, we reached the conclusion that Vietnamese population represent a new species for science which is here described and illustrated. We also provide a key to the species of Sterculia that are now known to occur in Vietnam.

Materials and methods

The morphology of the new species were observed on both living plants and herbarium specimens. Branches, leaves and (functionally female) flowers (lf, f. fl.) of type materials are stored at the Institute of Ecology and Biological Resources (HN) and the Institute of Tropical Biology (VNM) (acronyms follow Thiers 2023[continuously updated]). The conservation status of the new species was assessed according to the guidelines of the International Union for Conservation of Nature (IUCN 2019).

Taxonomy

Sterculia konchurangensis C.N.Kieu, D.B.Tran & B.H.Quang, sp. nov.

urn:lsid:ipni.org:names:77320206-1

Figs 1, 2, 3

Type

Vietnam. Tay Nguyen: Gia Lai province, Kon Chu Rang reserve, 1016 m a.s.l., 19 June 2022 (lf, f. fl.), Bui Hong Quang et al. BHQ 576 (holotype HN!, isotypes: HN!, VNM!).

Figure 1.

Sterculia konchurangensis C.N.Kieu, D.B.Tran & B.H.Quang A flowering branch B, C, D leaf blade E inflorescence F open flower showing androgynophore, ovary, style, stigma G androgynophore, staminodes, ovary, style, stigma H ovary, style, stigma I section ovary, style, stigma (Photos by D.B Tran).

Diagnosis

Sterculia konchurangensis is most similar to S. lanceolata Cav. due to the number of veins on each side of midrib, length of inflorescence, deeply divided calyx, globose, hairy ovary and curved style. They are separated by morphology of leaf blades (obovate or elliptic in S. konchurangensis vs. elliptic, lanceolate or elliptic-lanceolate in S. lanceolata); petioles are shorter (7.0–9.5 mm vs. 25–35 mm in S. lanceolata), leaf blades are shorter (6–8 cm vs. 9–20 cm in S. lanceolata) and calyx lobes are longer (11–12.5 mm vs. 4–6 mm in S. lanceolata).

Figure 2.

Sterculia konchurangensis C.N.Kieu, D.B.Tran & B.H.Quang A flowering branch B, C, D leaf blade E apex branches and stipules F inflorescence G flower H flower I open flower showing androgynophore, ovary, style, stigma J androgynophore, ovary, style, stigma, staminodes K section ovary, style, stigma (Drawn by Le Kim Chi).

Description

Shrubs , ca. 3 m tall. Branches gray brown. Leaves alternate, apically clustered; petiole 7.0–9.5 mm long, glabrous, base and apex of petiole swollen; leaf blade simple, entire, glabrous, obovate, elliptic, base attenuate, apex shortly acuminate or obtuse, 6–8 × 3–4 cm, both surfaces glabrous; lateral veins 6–8 on each side of midrib. Stipules linear, ca. 1–2 mm long. Inflorescence slender, racemose, axillary, 8 cm long, few-12 flowered. Pedicel slender, 9.5–12.0 mm long, densely villous. Flowers 5-merous, functionally unisexual. Flowers: Flower bud lanceolate, 6.3 × 2.3 mm. Calyx divided almost to base, 5-lobed, pink, adaxial surface nearly glabrous to sparsely pubescent, abaxial surface pubescent; tube 1.3–1.7 mm long; lobes linear-lanceolate, 11–12.5 × 2.5–2.8 mm. Petals absent. Androgynophore slender, curved, ca. 2 mm long, glabrous. Staminodes at top of androgynophore in whorl around base of carpels; anthers of staminodes ovate, 0.22 × 0.18 mm. Carpels 5; ovary globose, densely pubescent, 1.3–1.8 mm in diameter; style curved, 2–3 mm long, sparsely pubescent; stigma glabrous, 0.3–0.6 mm in diameter. Fruits and seeds not observed.

Figure 3.

Map indicating the type locality of Sterculia konchurangensis C.N.Kieu, D.B.Tran & B.H.Quang (Made by D.B Tran & T.B. Tran).

Etymology

The specific epithet refers to the type locality, Kon Chu Rang reserve in Vietnam.

Distribution and ecology

Sterculia konchurangensis is only found in Vietnam, Gia Lai province, Tay Nguyen area, Kon Chu Rang reserve where it grows in primary evergreen forest at an altitude of 1016 m a.s.l. Flowering time is June; fruiting time is unknown.

Conservation status

Data Deficient (DD; IUCN 2019). Sterculia konchurangensis is known only from the type locality within Kon Chu Rang reserve. A comprehensive botanical survey of the Sterculia has not been carried out to date.

Discussion

Sterculia konchurangensis is morphologically similar to S. lanceolata Cav. due to the number of veins on each side of midrib, length of the inflorescence, deeply divided calyx, globose, hairy ovary, and curved style; furthermore, to be noted that both species have the same flowering time (June). However, S. konchurangensis differs from S. lanceolata by the morphology of length of petiole, shape of leaf blade, size of leaf blade and length of calyx lobe.

The identified key of 23 species of Sterculia in Vietnam was constructed. Sterculia konchurangensis differs from 22 species of Sterculia by having some characters such as simple, entire, glabrous leaves and length of petiole (less than 12 mm long). In addition, the comparison with the similar species (S. lanceolata) confirms that S. konchurangensis is a new species. Diagnostic characters separating the two species are listed in Table 1.

Table 1.

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Morphological differences between S. lanceolata and S. konchurangensis.

Characters	S. lanceolata	S. konchurangensis
Length of petiole (mm)	25–35	7.0–9.5
Shape of leaf blade	elliptic, lanceolate or elliptic-lanceolate	obovate or elliptic
Size of leaf blade (cm)	9–20 × 3.5–8.0	6–8 × 3–4
Length of calyx lobe (mm)	4–6	11–12.5

Key to the species of Sterculia in Vietnam

1	Leaves palmately compound	2
–	Leaves simple	3
2	Calyx purple-red, ca. 12 mm long, divided nearly to base	*S. foetida*
–	Calyx white, ca. 6 mm long, divided to 1/2 of the total length	*S. pexa*
3	Leaf blade lobed	4
–	Leaf blade not lobed	5
4	Seeds 2 per follicle	*S. hypochroa*
–	Seeds 6–7 per follicle	*S. thorelii*
5	Basal veins 3–7	6
–	Basal veins absent	9
6	Leave base shallow cordate	*S. stigmarota*
–	Leave base not shallow cordate	7
7	Lateral veins 5–6 on each side of midrib	8
–	Lateral veins 7–10 on each side of midrib	*S. principis*
8	Seeds 1–2 per follicle	*S. lissophylla*
–	Seeds 3–6 per follicle	*S. chrysodasys*
9	Leave pubescent	10
–	Leaves glabrous	14
10	Leaves obovate or oblanceolate	11
–	Leaves elliptic-oblong	12
11	Lateral veins 16–24 on each side of midrib	*S. hymenocalyx*
–	Lateral veins less than 12 on each side of midrib	*S. parviflora*
12	Petiole 5–7 cm long	*S. radicans*
–	Petiole less than 4 cm long	13
13	Leaves silver hairy beneath	*S. pierrei*
–	Leaves rufous hairy beneath	*S. tonkinensis*
14	Petiole < 12 mm long	*S. konchurangensis*
–	Petiole > 15 mm long	15
15	The upper parts of the lateral veins connected	16
–	The upper parts of the lateral veins not connected	20
16	Lateral veins more than 6 pairs	17
–	Lateral veins 5–6-paired	*S. cochinchinensis*
17	Lateral veins less than 12 pairs	18
–	Lateral veins 12–15 paired	*S. henryi*
18	Petiole 2.5–8.0 cm long	19
–	Petiole 1–2 cm long	*S. hyposticta*
19	Calyx reddish, divided almost to base	*S. lanceolata*
–	Calyx dark brown, calyx united at the bottom 1/3	*S. aberrans*
20	Calyx 3.5–4.5 mm long	*S. gracilipes*
–	Calyx longer than 5 mm	21
21	Androgynophore longer than calyx tube	*S. bracteata*
–	Androgynophore shorter than calyx tube	22
22	Petiole 2–5 cm long	*S. monosperma*
–	Petiole 7–10 cm long	*S. scandens*

Acknowledgements

We thank the directors and curators of the herbaria HN, HNU, HNPM, P and VNM for allowing access to and/or for providing high quality images of herbarium specimens and to Le Kim Chi for the drawing. Funding for this research was provided by the project ĐTĐL.CN-72/22.

Additional information

Conflict of interest

No conflict of interest was declared.

Ethical statement

No ethical statement was reported.

Funding

No funding was reported.

Author contributions

Cam Nhung Kieu: Identification, description, key establishing and manuscript writing. Duc Binh Tran: Collection and description of species during fieldwork. Ngoc Han Le: Study on specimens at VNM herbarium. Thi Hoan Duong: Study on specimens at HN herbarium. Thu Ha Bui: Study on specimens at the other herbaria and related references. Thu Thuy Nguyen: Study on specimens at the other herbaria and related references. Hong Quang Bui: Collection and description of species during fieldwork. The Bach Tran: Identification, description, key establishing and manuscript correction.

Author ORCIDs

Cam Nhung Kieu https://orcid.org/0009-0002-7480-1030

Duc Binh Tran https://orcid.org/0000-0001-6658-0739

Ngoc Han Le https://orcid.org/0000-0003-2657-5091

Thi Hoan Duong https://orcid.org/0000-0002-4298-5720

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

Thu Thuy Nguyen https://orcid.org/0000-0002-0921-5652

Hong Quang Bui https://orcid.org/0000-0001-6878-7514

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

Data availability

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

References

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IUCN (2019) Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Subcommittee. http://cmsdocs.s3.amazonaws.com/RedListGuidelines.pdf

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