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Chayamaritia vietnamensis (Gesneriaceae), a new species from Son La Province, northern Vietnam
expand article infoZi-Bing Xin§|, Long-Fei Fu§|, Stephen Maciejewski§, Zhang-Jie Huang§, Truong Van Do#¤, Fang Wen§|
‡ Guangxi Institute of Botany, Guilin, China
§ Gesneriad Conservation Center of China, Guilin, China
| Gesneriad Committee, China Wild Plant Conservation Association, Guilin, China
¶ The Gesneriad Society, Philadelphia, United States of America
# Vietnam National Museum of Nature, Vietnam Academy of Science & Technology, Hanoi, Vietnam
¤ Graduate University of Science and Technology, Hanoi, Vietnam
Open Access

Abstract

Chayamaritia vietnamensis, a new species from Son La Province, northern Vietnam, is described and illustrated. The phylogenetic study revealed that the new species is most closely related to C. banksiae and C. smitinandii. The morphological comparison suggests it as the third new species of Chayamaritia and distinguished from C. banksiae and C. smitinandii by a combination of morphological characters of leaf blades, bracts, calyx and corolla, especially its peltate leaf blades. This species is provisionally assessed as endangered (EN B1ab(iii), B2ab(iii)) using IUCN Categories and Criteria. Information on ecology, phenology and an identification key for the known Chayamaritia species are also provided.

Keywords

Cliff-dwelling, Flora of Vietnam, new taxon, taxonomy

Introduction

The genus Chayamaritia D.J.Middleton & Mich.Möller (Gesneriaceae) was originally established and described, based on molecular and morphological data (Middleton et al. 2015). The genus Chayamaritia comprises two species and is hitherto known only in Laos and Thailand. A thickened rhizomatous prostrate stem, along with alternately arranged leaves and the imbricate sepals characterise the genus (Middleton et al. 2015). The type species, Chayamaritia smitinandii (B.L.Burtt) D.J.Middleton, was initially placed in the genus Chirita Buch.-Ham. (Burtt, 2001), then transferred to the genus Henckelia Spreng. (Weber et al. 2011) and eventually separated as a new genus in 2015, together with the newly-described species, Chayamaritia banksiae D.J.Middleton (Middleton et al. 2015). Chayamaritia banksiae and C. smitinandii are endemic to Laos and Thailand, respectively (Middleton et al. 2015).

During a joint Sino-Vietnamese botanical survey for plant biodiversity in northern Vietnam in late October 2019, we collected an unknown Gesneriaceae plant. In the Xuan Nha Nature Reserve, Moc Chau District, Son La Province, northern Vietnam, we discovered this plant that looked like a Chayamaritia species. Detailed comparison of these specimens with the type specimens and protologues of known Chayamaritia species showed that these specimens neither fitted the existing protologues nor conformed to the type specimens of these species. Although, the leaf indumentum and inflorescence of the unknown plant was most similar to those of C. banksiae and C. smitinandii, it could be easily distinguished from the latter two by the combination of several morphological characters of the leaf blades, bracts, calyx and corolla, especially its peltate leaf blade. Thus, we confirmed that it represented a new species of Chayamaritia, which is the first Chayamaritia species from Vietnam. The description, illustration, information on ecology, phenology and provisional conservation assessment using IUCN (2019) of the proposed new species are provided. Furthermore, an identification key to the known Chayamaritia species is given.

Material and methods

Plant material

Herbarium materials were studied from the following herbaria: E, IBK, US and VNMN (herbarium acronyms according to Index Herbariorum; Thiers 2019). The macromorphological features were observed, based on the specimen sheets and notes in both the field and the conservation nursery at the Gesneriad Conservation Center of China and the National Gesneriaceae Germplasm Bank at GXIB. Micromorphological features were analysed and photographed using an optical microscope (Stemi DV4, LEICA S8 AP0, Jena, Germany).

These morphological characters of newly-proposed species were compared with those of the two known Chayamaritia species from protologues, type specimens and living plants. The description of the new species followed the terminology used by Harris and Harris (2001) and Wang et al. (1998). Assessment of the conservation status of the new species was according to Categories and Criteria of the IUCN (2019).

DNA extraction, PCR amplification and sequencing

Leaves were dried using silica gel for DNA extraction (Chase and Hills 1991). Genomic DNA was extracted using the CTAB protocol (Doyle and Doyle 1987). To confirm the placement of this new species, we performed phylogenetic studies of DNA sequence data obtained from the nuclear ribosomal internal transcribed spacer (ITS) region and the plastid trnL-F intron spacer (trnL-F). Given the phylogenetic studies of Middleton et al. (2015), we sampled two species (three accessions) from Chayamaritia and the new species as ingroup and ten species from all closely related and morphologically similar genera, including Allostigma (one species), Deinostigma (two species), Loxostigma (two species), Petrocosmea (two species), Pseudochirita (two varieties) and Primulina (two species) as outgroup (Middleton et al. 2015). DNA extraction, PCR amplification and sequencing were performed following Wei et al. (2013). The species name, voucher specimens and GenBank accession numbers of DNA sequences used in this study are listed in Table 1.

Table 1.

Species names, voucher specimens, and GenBank accession numbers of DNA sequences used in this study.

Species name Voucher number Herbarium Origin ITS trnL-F
Allostigma guangxiense W.T.Wang M. Möller and Y.G. Wei MMO 05-755 E, IBK China, Guangxi, Longzhou county HQ632977 HQ632880
Deinostigma cicatricosa (W.T.Wang) D.J.Middleton & Mich.Möller W. B. Xu s.n. [XWB] IBK China, unknown locality JX506925 JX506817
Deinostigma cyrtocarpa (D.Fang & L.Zeng) Mich.Möller & H.J.Atkins M. Möller and Y.G. Wei MMO 06-908 E, IBK China, Guangxi, He Zhou city KU990889 KU990885
Pseudochirita guangxiensis (S.Z.Huang) W.T.Wang M. Möller and Y.G. Wei MMO 06-798 E, IBK China, Guangxi, Mashan county HQ633003 HQ632908
Pseudochirita guangxiensis (S.Z.Huang) W.T.Wang var. glauca Y.G.Wei & Yan Liu M. Möller and Y.G. Wei MMO 05-751 E, IBK China, Guangxi, Jingxi county HQ633004 HQ632909
Loxostigma glabrifolium D.Fang & K.Y.Pan Y.G. Wei 709 IBK China, Guangxi, Napo county HQ633006 HQ632910
Loxostigma griffithii (Wight) C.B.Clarke Kew/Edinburgh Kanchenjunga Expedition (1989) 940 [Cult. RBGE 19892473A] E Nepal, Yamphudin FJ501338 FJ501508
Chayamaritia banksiae D.J.Middleton D.J. Middleton 5220 and M. Newman et al. LAO1428 E Laos, Khammouan, Nakai Nam Theun KP325426 KP325433
Chayamaritia smitinandii (B.L.Burtt) D.J.Middleton & Mich.Möller D.J. Middleton et al. 5632 E Thailand, Nakhon Nayok, Khao Yai NP KP325424 KP325431
Chayamaritia smitinandii (B.L.Burtt) D.J.Middleton & Mich.Möller D.J. Middleton et al. 5652 E Thailand, Nakhon Nayok, Khao Yai NP KP325425 KP325432
Chayamaritia vietnamensis F.Wen, T.V.Do, Z.B.Xin & S.Maciej F. Wen, T.V. Do, Z.B. Xin & S. Maciejewski, VMN-CN1214 IBK, VNMN Vietnam, Son La, Moc Chau MW458944* MW458945*
Petrocosmea kerrii Craib Voucher from Cult. RBGE 19715592 E unknown origin FJ501334 FJ501502
Petrocosmea nervosa Craib Smithsonian Institute 78-057 [Cult. RBGE 19933232] E, US China, N Yunnan FJ501335 AJ492299
Primulina tabacum Hance Q.J. Xie and C.X. Ye s.n. [Cult. RBGE 19951540] E E China, Guangdong, Lian Rive FJ501352 AJ492300
Primulina gemella (D.Wood) Yin Z.Wang L. Averyanov 1987 [Cult. RBGE 19941913] E Vietnam, Hong Quang Special Region, Cat Hai FJ501345 FJ501523

Phylogenetic analysis

The sequence data were edited and assembled using Lasergene Navigator 7.1 (DNAstar, Madison, Wisconsin, USA). Two datasets (ITS and trnL-F) were aligned independently using MAFFT version 7.0 (Katoh and Standley 2013) with default settings. The two best-supported tree topologies from Maximum Likelihood (ML) analyses of ITS and trnL-F were compared visually for topological incongruences. As there were no hard incongruences (Nishii et al. 2015), phylogenies were reconstructed, based on the combined dataset using ML and Bayesian Inference (BI). BI was performed using MRBAYES v.3.2.7 (Ronquist et al. 2012). Best-fitting models for the BI analysis were obtained independently for each gene region using MODELTEST v.3.7 (Posada and Buckley 2004). GTR+G and GTR+I were the best-fitting models for ITS and trnL-F, respectively. One cold and three incrementally heated Markov Chain Monte Carlo (MCMC) chains were run for five million generations and trees were sampled every 1,000 generations (5,000 trees sampled in total). The first 1250 trees (25%) were discarded as burn-in prior to calculating the BI consensus trees and posterior probabilities (PP) (See Suppl. material 1: log file). The ML analyses were performed in RAxML using raxmlGUI (Silvestro and Michalak 2012), with GTRGAMMA setting and 1,000 bootstrap replicates.

Results

The combined ITS and trnL-F matrix was 1,477 characters long (700 for ITS and 777 for trnL-F). Of the 378 variable characters, 155 (56.97%) were parsimony-informative. ML and BI analyses resulted in the same tree topology indicating the undescribed species as sister to the two known Chayamaritia species (BS = 97%, PP = 1), i.e. C. banksiae and C. smitinandii (Fig. 1).

Figure 1. 

Phylogenetic tree of Chayamaritia and related genera generated from the Maximum Likelihood analysis (ML) of the combined dataset (ITS and trnL-F). Numbers on the branches indicate bootstrap values (≥ 50%) of the ML and the posterior probability (≥ 0.5) of the BI analyses. Created by Long-Fei Fu.

Taxonomic treatment

Chayamaritia vietnamensis F.Wen, T.V.Do, Z.B.Xin & S.Maciej, sp. nov.

Figs 2, 3C

Diagnosis

The new species can be easily distinguished from the known Chayamaritia species by its peltate leaf blades. Besides, it differs from C. banksiae by its leaf blades apex rounded and margin entire (vs. apex shortly acuminate and margin minutely dentate); bracts 3, apex rounded and margin entire (vs. 2, apex acuminate and margin dentate); calyx lobes inside glabrous and margin entire (vs. inside with white appressed hairs in upper half, margin coarsely dentate); corolla lobes margin entire (vs. margin being minutely dentate); lateral staminodes 2.5–4 mm long (vs. 5.5–11 mm long). It also differs from C. smitinandii by its leaf blades apex rounded and margin entire (vs. apex acuminate and margin minutely dentate); bracts 3, ovate narrow and apex rounded (vs. 2, narrowly elliptic to lanceolate, somewhat falcate, apex acuminate); calyx lobes inside glabrous and margin entire (vs. inside densely pubescent, margin slightly toothed or appearing as large sessile glands on margin).

Type

Vietnam. Son La Province: Moc Chau District, Xuan Nha Nature Reserve, 20°43'N, 104°40'E, elev. ca. 850 m, 31 October 2019, F. Wen, T.V. Do, Z.B. Xin & S. Maciejewski, VMN-CN1214 (Holotype: VNMN!; Isotypes: IBK!, VNMN!).

Description

Herbs perennial, rhizomatous prostrate thickened stem. Leaves basal, alternately arranged, numerous; petioles cylindrical, 10–25 cm long, 6–8 mm in diameter, densely covered with short white appressed hairs; leaf blade ovate to elliptic, peltate, 12–20 × 10–15 cm, 1.2–1.3 times as long as wide, both surfaces densely covered with short white appressed hairs, base rounded, apex rounded, margin entire; lateral veins 6–9 on each side of the mid-rib, impressed on the adaxial surface, prominent on the abaxial surface. Inflorescences cymose, all axes and bracts pale green with red appressed hairs; cymes 4–6, axillary, 1–3-branched, 2–12-flowered; peduncle 15–25 cm long, 4–6 mm in diameter, scattered villous; bracts 3, narrow ovate, 1.3–1.6 cm long, 5–6 mm wide, adaxially sparsely villous, abaxially densely villous, margin entire, apex rounded; pedicel 2.5–3.5 cm long, 1.5–2 mm in diameter, spreading puberulent. Calyx 5-parted nearly to the base, strongly imbricate; lobes ovate, ca. 1.3 cm long, ca. 6 mm wide, appressed villous outside, glabrous inside, margin entire, apex acuminate. Corolla 5.5–6.5 cm long, dark purple throughout outside, white to pale purple with two parallel yellow lines ventrally inside, lobes purple outside and inside, paler at base; tube 3.5–4 cm long, 1–1.2 cm in diameter at the mouth, 6–8 mm in diameter at the base; limb distinctly 2-lipped, adaxial lip 2-parted to over middle, lobes ca. 1 × 1 cm, orbicular; abaxial lip 3-parted to near the middle, lobes 1.3–1.5 × ca. 1 cm, oblong. Stamens 2, adnate to ca. 2.2 cm above the base of the corolla tube; filaments 1–1.2 cm long, white, sparsely pubescent, strongly geniculate at ca. 5 mm above the filament base, anthers ca. 2 mm long, sparsely pubescent. Staminodes 3, lateral ones 2.5–4 mm long, white, glabrous, adnate to 1.8 cm above the base of the corolla tube, the middle one ca. 0.5–1 mm long, adnate to 1.2 cm above the base of the corolla tube. Disc orbicular, ca. 3 mm in height, 5-crenate at the margin, glabrous. Pistil 4–4.5 cm long, ovary 2.5–2.8 cm long, 2–2.5 mm in diameter, mixed pubescent and glandular-pubescent; style 1–1.2 mm long, ca. 0.6 mm in diameter, mixed pubescent and glandular-pubescent; stigma only of lower lobe, bifid with blunt lobes, lobe ca. 3 mm long, ca. 0.5 mm in diameter. Capsules straight, 5.5–6.5 cm long, ca. 3.5–4 mm in diameter.

Figure 2. 

Chayamaritia vietnamensis F.Wen, T.V.Do, Z.B.Xin & S.Maciej A, B habitat C habit D adaxial (top) and abaxial (bottom) surface of leaf blade E cymes F peduncle G adaxial (top) and abaxial (bottom) surface of bracts H pistil, calyx and lateral view of corolla I opened corolla with stamens and staminodes J stamens with cohering anthers K pistil L adaxial (top) and abaxial (bottom) surface of calyx lobes. Photos by Fang Wen, arranged by Zi-Bing Xin.

Phenology

Flowering occurs from October to December and fruiting from November to January.

Etymology

The specific epithet “vietnamensis” is derived from Vietnam, which holds the first discovered and only known location for the species.

Figure 3. 

Three species of Chayamaritia A C. banksiae D.J.Middleton B C. smitinandii (B.L.Burtt) D.J.Middleton C C. vietnamensis F.Wen, T.V.Do, Z.B.Xin & S.Maciej. Photos by Fang Wen, arranged by Zi-Bing Xin.

Distribution and habitat

Chayamaritia vietnamensis is hitherto only known from the type locality, Xuan Nha Nature Reserve, Moc Chau District, Son La Province, northern Vietnam. It grows on rock surfaces surrounded by limestone areas in a subtropical evergreen seasonal rain forest.

Conservation status

Chayamaritia vietnamensis is known from two small-sized populations in the Xuan Nha Nature Reserve’s buffer zone. The EOO and AOO of the new species are about 6.15 km2 and 2.2 km2, respectively. Furthermore, the natural habitat is mostly disturbed by local farmers who impose intense pressure on the remaining primary forest patches, by converting the natural habitat of the species into cornfields. Thus, following the IUCN Red List Categories and Criteria (IUCN 2019), it is provisionally assessed as endangered (EN B1ab(iii), B2ab(iii))

Identification key for the three known Chayamaritia species (Fig. 3)

1 Leaf blade peltate, apex rounded, margin entire C. vietnamensis
Leaf blade not peltate, apex acuminate, margin minutely dentate 2
2 Calyx lobes 7–15 mm wide, corolla tube white ventrally C. banksiae
Calyx lobes 0.9–4.2 mm wide, corolla tube purple ventrally C. smitinandii

Discussion

From the viewpoint of morphology, the newly-described species should be treated as a species of Chayamaritia, because it exhibits a suite of morphological characters that are diagnostic to the genus and should not be established as a distinct genus. It has a thickened rhizomatous prostrate stem, alternately arranged leaves and imbricate sepals (Middleton et al. 2015). The current molecular work also confirmed that the new species is sister to a clade comprising the two known Chayamaritia species (C. banksiae and C. smitinandii). A detailed morphological comparison of the new species with its two relatives is summarised in Table 2. This new species is the first Chayamaritia species reported from Vietnam. In order to facilitate identification, we also provide an identification key to all known Chayamaritia species.

Table 2.

Morphological comparison of Chayamaritia vietnamensis and its two relatives.

Characters C. vietnamensis C. banksiae C. smitinandii
Leaf blade peltate, 1.2–1.3 times as long as wide, apex rounded, margin entire palaceous, 1.5–1.9 times as long as wide, apex shortly acuminate, margin minutely dentate palaceous, 1.8–5.6 times as long as wide, apex acuminate, margin minutely dentate
Bracts 3, narrow ovate, 5–6 mm wide, apex rounded, margin entire 2, ovate, 19 mm wide, apex acuminate, margin dentate 2, narrowly elliptic to lanceolate, somewhat falcate, 1.8–8 mm wide, apex acuminate, margin entire
Pedicels 25–35 mm long 12–15 mm long 6.5–11 mm long
Calyx lobes 4–6 mm wide, inside glabrous, margin entire 7–15 mm wide, inside with white appressed hairs in the upper half, margin coarsely dentate 0.9–4.2 mm wide, inside densely pubescent, margin slightly toothed or appearing as large sessile glands on margin
Corolla outside dark purple throughout, lobes margin entire outside white ventrally, lobes being minutely dentate along the margin outside deep purple throughout, lobes margin entire
Lateral staminodes 2.5–4 mm long 5.5–11 mm long 4–5 mm long
Disc ca. 3 mm high ca. 1.5 mm high 0.9–1.4 mm high

Conclusion

In the present study, we discovered and described a new species of Chayamaritia from Vietnam, based on both morphological and molecular evidence. This newly-described species further suggests floristic similarities amongst countries of the Indochinese Peninsula. Our new finding provides an essential addition to the ongoing project of ‘Flora of Vietnam’ and ‘Flora of Cambodia, Laos and Vietnam’.

Acknowledgements

We want to thank the staff from Xuan Nha Nature Reserve for guiding our investigation and collecting the specimens. We also want to thank Michael LoFurno, Adjunct Professor, Temple University, Philadelphia, USA, for his editorial assistance. This study was financially supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) (106.03-2019.308), the Foundation of Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain (19-050-6; 19-185-7), the National Natural Science Foundation (31860047), Guilin Science and Technology Foundation (20180107-6), the Key Science and Technology Research and Development Project of Guangxi (Guike AD20159091), Guangxi Natural Science Foundation (2020GXNSFBA297049), Basal Research Fund of GXIB (Guizhiye20009) and the 21st Talent project of “Ten-Hundred-Thousand” in Guangxi.

References

  • Burtt BL (2001) Thailand-annotated checklist of Gesneriaceae. Thai Forest Bulletin (Botany) 29: 81–109.
  • Chase MW, Hills H (1991) Silica gel: An ideal material for field preservation of leaf samples for DNA studies. Taxon 40(2): 215–220. https://doi.org/10.2307/1222975
  • Doyle JJ, Doyle JL (1987) A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochemical Bulletin 19: 11–15.
  • Harris JG, Harris MW (2001) Plant Identification Terminology: An Illustrated Glossary (2nd ed.). Spring Lake Publishing, Payson, 216 pp.
  • Katoh K, Standley DM (2013) MAFFT multiple sequence alignment software version 7: Improvements in performance and usability. Molecular Biology and Evolution 30(4): 772–780. https://doi.org/10.1093/molbev/mst010
  • Middleton DJ, Nishii K, Puglisi C, Forrest LL, Möller M (2015) Chayamaritia (Gesneriaceae: Didymocarpoideae), a new genus from southeast Asia. Plant Systematics and Evolution 301(7): 1947–1966. https://doi.org/10.1007/s00606-015-1213-2
  • Nishii K, Hughes M, Briggs M, Haston E, Christie F, DeVilliers JM, Hanekom T, Roos GW, Bellstedt UD, Möller M (2015) Streptocarpus redefined to include all Afro-Malagasy Gesneriaceae: Molecular phylogenies prove congruent with geography and cytology and uncovers remarkable morphological homoplasies. Taxon 64: 1243–1274. https://doi.org/10.12705/646.8
  • Posada D, Buckley T (2004) Model selection and model averaging in phylogenetics: Advantages of Akaike Information Criterion and Bayesian approaches over likelihood ratio tests. Systematic Biology 53(5): 793–808. https://doi.org/10.1080/10635150490522304
  • Ronquist F, Teslenko M, Van Der Mark P, Ayres DL, Darling A, Höhna S, Larget B, Liu L, Suchard MA, Huelsenbeck JP (2012) MrBayes 3.2: Efficient Bayesian phylogenetic inference and model choice across a large model space. Systematic Biology 61(3): 539–542. https://doi.org/10.1093/sysbio/sys029
  • Thiers B (2019) Index Herbariorum: a global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. http://sweetgum.nybg.org/ih [Accessed 10 August 2020]
  • Wang WT, Pan KY, Li ZY, Weitzman AL, Skog LE (1998) Gesneriaceae. In: Wu ZY, Raven PH (Eds) Flora of China (Vol. 18). Science Press, Beijing & Missouri Bot Garden, St. Louis.
  • Weber A, Middleton DJ, Forrest A, Kiew R, Lim CL, Rafidah AR, Sontag S, Triboun P, Wei YG, Yao TL, Möller M (2011) Molecular systematics and remodelling of Chirita and associated genera (Gesneriaceae). Taxon 60(3): 767–790. https://doi.org/10.1002/tax.603012
  • Wei YG, Wen F, Zhao B, He SZ (2013) Anna rubidiflora (Gesneriaceae), a new species from Guizhou, the southern part of China. Plant Ecology and Evolution 146(2): 203–211. https://doi.org/10.5091/plecevo.2013.731