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Research Article
Rungia fangdingiana (Acanthaceae), a new species from Guangxi, China
expand article infoZhe-Li Lin‡, Yun-Hong Tan§|, Yun-Feng Huang, Yun-Fei Deng‡|#
‡ South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
§ Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, China
| Research Institute, Chinese Academy of Sciences, Nay Pyi Taw, Myanmar
¶ Guangxi Institute of Traditional Medical and Pharmaceutical Sciences, Nanning, China
# Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China

Corresponding author: Yun-Fei Deng ( yfdeng@scib.ac.cn )

Academic editor: Alan Paton
© 2022 Zhe-Li Lin, Yun-Hong Tan, Yun-Feng Huang, Yun-Fei Deng.
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: Lin Z-L, Tan Y-H, Huang Y-F, Deng Y-F (2022) Rungia fangdingiana (Acanthaceae), a new species from Guangxi, China. PhytoKeys 202: 97-105. https://doi.org/10.3897/phytokeys.202.86653
Open Access

Abstract

Rungia fangdingiana, a new species of Acanthaceae from Guangxi, China is described and illustrated. This new species belongs to Rungia sect. Rungia, and resembles R. sinothailandica and R. burmanica in the erect perennial herbaceous habit, elliptic leaves and inflorescence form, but differs mainly by the indumentum and the morphology of the bracts and corolla. The pollen and seed micromorphology of this new species are studied, with photographs and a line drawing provided.

Keywords

limestone, SEM, taxonomy, tricolporate pollen

Introduction

Rungia Nees is a genus of Acanthaceae, comprising about 50 species and distributed through tropical and subtropical regions of the Old World (Mabberley 2017). It is closely related to Justicia L., but differs from the latter mainly by the rising placenta in ripe fruit (Hansen 1989; Hu 2002; Hu et al. 2011; Kiel et al. 2017; Deng 2020; Deng and Gao 2020). Some Rungia species were transferred to Justicia in regional Floras (Darbyshire et al. 2010; Wood 2014; Vollesen 2015), but the recent systematic studies (Kiel et al. 2017; Manzitto-Tripp et al. 2021) do not agree with this treatment based on molecular and some morphological evidence. In this work, we treat Rungia as a separate genus; however, the relationship between Rungia and its related genera is awaiting further study.

Sixteen species of Rungia were recognized in the “Flora of China” (Hu et al. 2011). Amongst these, R. monetaria (Benoist) B. Hansen was misidentified (the collection is actually R. flaviflora) and should be excluded from the list of species found in China, R. axilliflora and R. densiflora were treated as synonyms of R. stolonifera (Lin et al. 2020), Whereas R. burmanica (C. B. Clarke) B. Hansen is newly recorded in China (Lin and Deng 2017a, 2018), and recently two new species, Rungia sinothailandica Z. L. Lin & Y. F. Deng and R. flaviflora Z. L. Lin & Y. F. Deng, were described (Lin and Deng 2017b, 2018). Consequently, sixteen species of Rungia are still recognized in China at present.

During examination of the specimens in Herbaria (HITBC, PE), a distinctive specimen (H. Wang 6616) collected from Napo County, Guangxi in 2002, attracted our attention because of its secund spike, which is the typical character of the genus Rungia, but it lacked flower and fruit. Recently, it was collected again in the field complete with flowers and fruits from Napo in 2015 (Y. H. Tan et al. 4366) and 2019 (Y. F. Deng et al. 29030). After careful study of the specimens and living plants, we confirmed that it represents a new species of Rungia and is described below.

Materials and methods

The morphological description of the new species was based on both fresh and dried materials. The voucher specimens (Y. H. Tan et al. 4366, Y. F. Deng et al. 29030 and H. Wang 6616) are deposited in the Herbaria of South China Botanical Garden, Chinese Academy of Sciences (IBSC), Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences (HITBC) and Institute of Botany, Chinese Academy of Sciences (PE).

The pollen and seeds were washed in 70% alcohol and then gilded using the auto-fine sputter coater (JEOL JFC-1600 Auto Fine Coater, Japan). The micrographs were taken using the scanning electron microscope (JEOL Model JSM-6360 LV, Japan). The polar (P) axis and equatorial (E) diameter of 20 pollen grains were measured and the average, maximum, minimum and ratio (P/E) values were recorded to represent the range of variation. The pollen terminology follows Daniel (1998) and Scotland and Vollesen (2000). The seed terminology follows Graham (1988).

Taxonomic treatment

Rungia fangdingiana Z. L. Lin, Y. F. Deng & Y. H. Tan, sp. nov.

urn:lsid:ipni.org:names:77302500-1
Figs 1, 2, 3

Type

China. Guangxi Province: Napo County, Baisheng Xiang, Nongmiao Cun, 965 m elev., 24 July 2015, Y. H. Tan et al. 4366 (holotype: IBSC!; isotypes: IBSC!, HITBC!).

Diagnosis

Similar to Rungia sinothailandica and R. burmanica, but is readily distinguishable by the flat, entire bract margin (vs. crispate, tawny membranous bract margin in R. sinothailandica, and crenulate bract margin in R. burmanica), glabrous calyx and capsule (vs. puberulous calyx and puberulent capsule in R. sinothailandica and R. burmanica), pale yellow corolla with red stripes, upper lip unlobed (vs. white corolla with red stripes, upper lip 2-lobed in R. sinothailandica, and white corolla with purple dotted stripes, upper lip unlobed in R. burmanica). A detailed comparison of the three species is given in Table 1.

Table 1.
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Morphological comparison of Rungia fangdingiana, R. sinothailandica and R. burmanica.

Characters R. fangdingiana R. sinothailandica R. burmanica
Stem glabrous bifariously pubescent glabrous
Leaves glabrous pubescent glabrous
Sterile bract without membranous margin, margin entire membranous margin crispate, hyaline with slightly tawny colour, 1.5 mm wide without membranous margin, margin crenulate towards the apex
Fertile bract rhombic to elliptic, membranous margin flat and hyaline, 0–0.5 mm wide, margin entire obovate to elliptic, membranous margin crispate, hyaline at base and tawny at apex, 2 mm wide obovate, without membranous margin, margin crenulate towards the apex
Calyx lobes linear, glabrous lobes linear, puberulous lobes linear, puberulous
Corolla pale yellow with red stripes, upper lip unlobed white with red stripes, upper lip 2-lobed white with purple dotted stripes, upper lip unlobed
Capsule glabrous puberulent puberulent
Figure 1. 

Photographs of Rungia fangdingiana sp. nov. A habit B spike (abaxial view showing the sterile bracts) C spike (adaxial view showing the fertile bracts and fruits) D spike (adaxial view showing the fertile bracts and corolla) E corolla F, G adaxial view of leaf blade (showing the linear cystoliths) A–E by Yun-Hong Tan, F, G by Zhe-Li Lin.

Description

Perennial erect herb, about 1 m tall. Stem terete, glabrous. Leaves usually anisophyllous; petiole 1–2 cm long, glabrous; blade elliptic, 5–15 × 2–5 cm, base cuneate, margin entire, apex attenuate or acute, both surfaces glabrous, but densely covered with linear cystoliths, secondary veins 5–10 on each side of mid-vein. Inflorescence of terminal and axillary spikes, 3–7 cm long; peduncle 1–2 cm long, glabrous. Bracts 4-ranked, only two ranks fertile; sterile bracts ovate, oblique at base, 1.4–1.6 × 0.9–1.1 cm, green, glabrous, both surfaces covered with linear cystoliths, lacking hyaline margins; fertile bracts rhombic to elliptic, symmetrical, 1.3–1.5 × 0.9–1.1 cm, green, glabrous, both surfaces covered with linear cystoliths, membranous hyaline margin flat, 0–0.5 mm wide. Bracteoles elliptic, 1.0–1.1 × 0.3–0.4 cm, green, glabrous, abaxial surface covered with linear cystoliths, membranous hyaline margin flat, sometimes slightly puberulent at margin, ca. 1 mm wide. Calyx 5-lobed almost to the base, lobes linear, equal, 8–8.5 × 0.9–1.1 mm, glabrous. Corolla bilabiate, glabrous, ca. 1.5 cm long, pale yellow with red stripes on lower lip and throat; tube cylindrical at base and enlarged abruptly in throat, ca. 1 cm long; upper lip unlobed, attenuate at apex; lower lip 3-lobed, lobes rounded at apex. Stamens 2, 4.5–5 mm long, inserted at base of corolla throat, base adnate with corolla tube; filaments glabrous; anthers bithecous, superposed, ca. 3 mm long, thecae ovoid, glabrous, lacking a conspicuous basal spur. Pollen prolate, 35.99 (33.2–38.5) × 18.94 (15.7–21.6) μm, with P/E = 1.90, tricolporate, with one row of insulae on each side of aperture, exine ornamentation reticulate. Ovary glabrous, ca. 1.5 mm long; style slightly puberulent at base and middle part, ca. 1 cm long; stigma minutely 2-lobed. Capsule clavate, stipitate, glabrous, 1.1–1.2 × 0.3–0.35 cm. Seeds suborbicular to elliptic, compressed, dark brown, 2.5–3.5 × 2–2.5 mm, surface covered with brain-like verrucae.

Figure 2. 

Fruit, seed and pollen morphology of Rungia fangdingiana sp. nov. A dehiscent capsule (showing the rising placenta and seeds) B seed C seed testa (SEM) D detail of the verrucae of seed testa (SEM) E interapertural view of pollen grain F apertural view of pollen grain. Photos by Zhe-Li Lin.

Phenology

It was observed with flower and fruit at the same time from October to December and June to July.

Etymology

This new species is named in honor of Mr. Fang Ding (1924–2017) for his contributions to studies of the family Acanthaceae from Guangxi, China. He was the co-author of the account of family Acanthaceae for “Flora of Guangxi” and has published 37 new taxa of Acanthaceae from Guangxi (Fang and Deng 2017).

Vernacular name

方鼎孩儿草 (Chinese pinyin: fāng dǐng hái ér cǎo).

Distribution and habitat

This species is currently known from three localities in Napo County of Guangxi Province. It grows close to stream sides in evergreen forest on limestone at elevations of 600 to 1200 m.

Conservation status

During the field investigations, only three scattered populations of Rungia fangdingiana were discovered, which all grow in forest on limestone in Napo county. Because of its narrow distribution (extent of occurrence < 20,000 km2), limited locations (< 10), with an estimated population size of < 1000 mature individuals, and there is continuing decline estimated in quality of habitat and number of locations due to human activities as the localities are not protected, it should be assessed as Vulnerable (VU) (B1ab(iii)(iv)) according to the IUCN Red List Categories and Criteria (IUCN 2012, 2022). However, the area around the localities of this new species is poorly investigated, and further rigorous investigations are necessary to confirm this assessment.

Figure 3. 

Line drawings of Rungia fangdingiana sp. nov. A flowering branch B spike (abaxial view showing the sterile bracts) C spike (adaxial view showing the fertile bracts and corolla) D sterile bract E fertile bract F bracteole (abaxial view) G bracteole (adaxial view) H calyx I corolla J opened corolla K pistil L stigma M stamen (adaxial view) N stamen (abaxial view) O dehiscent capsule (showing the rising placenta and seeds) P seed. Drawn by Yun-Xiao Liu.

Additional specimens examined

(paratypes): China. Guangxi, Napo County: Nonghe Cun, on the way from Nonghe Cun to Tongziwan Power Station, on the rocks near stream-sides, 674 m elev., 11 December 2019, Y. F. Deng et al. 29030 (IBSC!); Napo County, in limestone forest, 1200 m elev., 24 October 2002, H. Wang 6616 (HITBC!, PE!).

Discussion

Rungia fangdingiana fits well with the circumscription of Rungia sect. Rungia according to the infrageneric classification by Gao and Deng (2007), as its flowers are arranged in a secund spike with heteromorphic bracts in two ranks of fertile bracts and two ranks of sterile bracts. Among the species in Rungia sect. Rungia, this new species is morphologically most similar to Rungia sinothailandica and R. burmanica, a key to these three similar species are provided as below.

Key to Rungia fangdingiana and morphologically similar species in China

1 Bracts with a crispate, tawny margin, upper lip of corolla 2-lobed R. sinothailandica
– Bracts lacking a crispate, tawny margin, upper lip of corolla unlobed 2
2 Calyx and capsule glabrous; corolla pale yellow with red stripes R. fangdingiana
– Calyx and capsule puberulous; corolla white with purple dots R. burmanica

Previously, the pollen morphology of ten species were reported in Rungia (Raj 1961, 1965; Scotland and Vollesen 2000; Rueangsawang et al. 2013; Lin et al. 2016; Lin and Deng 2017b, 2018; Kiel et al. 2017), amongst which nine species have dicolporate pollen grains and one species (Rungia flaviflora) has tricolporate pollen grains. In this study, R. fangdingiana is the second species found to have tricolporate pollen grains in Rungia.

The seed micromorphology of the four species in Rungia has been reported previously (Rueangsawang et al. 2012; Lin et al. 2016; Kiel et al. 2017; Lin and Deng 2017b), with two species having volcano-like verrucae on the seed testa, one species having brain-like verrucae, and R. repens was not observed under SEM (Kiel et al. 2017) so the detail of verrucae is not clear. The seed testa of R. fangdingiana has brain-like verrucae.

The micromorphology of pollen and seed is important in taxonomy in the family Acanthaceae (Radlkofer 1883; Lindau 1895; Raj 1961; Graham 1988; Daniel 1998; Scotland and Vollesen 2000; Cui and Hu 2005; Hu et al. 2005a, 2005b; Rueangsawang et al. 2012, 2013; Kiel et al. 2017; Manzitto-Tripp et al. 2021). However, due to the limited number of species studied in Rungia, further studies on pollen and seed morphology are necessary to understand its significance in species delimitation and the systematics in this genus.

Acknowledgements

We are grateful to the curators of the Herbaria of HITBC, IBSC and PE for access to the specimens for our study and to Mrs. Yun-Xiao Liu (IBSC) for preparing the line drawings. This work was supported by the National Natural Science Foundation of China (Grant No. 31900182, 31970208), Guangdong Natural Science Foundation (Grant No. 2018A030310390) and Guangxi Chinese Medicine Key Disciplines Construction Projects (GZXK-Z-20-69).

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