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Research Article
Primulina flexusa sp. nov. (Gesneriaceae) from Guizhou Province, China
expand article infoTao Peng‡, Bo Pan§|, Stephen Maciejewski§, Fang Wen|#
‡ Guizhou Normal University, Guiyang, China
§ Gesneriad Conservation Center of China, Guilin, China
| Guangxi Institute of Botany, Guilin, China
¶ The Gesneriad Society, Seattle, United States of America
# Guilin Botanical Garden, Guilin, China

Corresponding author: Fang Wen ( wenfang760608@139.com )

Academic editor: Eberhard Fischer
© 2020 Tao Peng, Bo Pan, Stephen Maciejewski, Fang Wen.
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: Peng T, Pan B, Maciejewski S, Wen F (2020) Primulina flexusa sp. nov. (Gesneriaceae) from Guizhou Province, China. PhytoKeys 159: 61-69. https://doi.org/10.3897/phytokeys.159.55386
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Abstract

The limestone regions of Yunnan-Guangxi-Guizhou in southern and southwestern China are regarded as some of biodiversity’s hotspots for China’s Gesneriaceae where numerous rare new species of Primulina have been, or are being, described over the past two decades. Primulina flexusa, a new lithophytic species of Gesneriaceae from a limestone hill in a Karst area, from Guizhou, China, is described here with color photographs. It is similar to P. curvituba, but can be easily distinguished by a combination of characteristics, especially in the shape and length of its capsule. We found only one population with approximately 100 mature individuals at the type locality. This new species is provisionally assessed as Critically Endangered [CR C1] by using IUCN criteria.

Keywords

Cliff-dwelling, flora of Guizhou, limestone flora, lithophytic, taxonomy

Introduction

The vast majority of Primulina species have a straight funnelform-tubular to campanulate or cylindric corolla tube (Wang et al. 1990, 1998; Li and Wang 2005). They usually are not swollen or gibbous abaxially. However, there are some exceptions; for example, in the past decade, some newly published species of Primulina have an inflated corolla tube, like P. crassituba (W.T. Wang) Mich. Möller and A. Weber (Wang 1989), P. carinata Y.G. Wei, F. Wen & H.Z. Lü (Wen et al. 2014) and P. inflata Li.H. Yang & M.Z. Xu (Xu et al. 2020). Another rare corolla characteristic of Primulina is the curved tube. So far, before this new taxon was discovered, only one species of Primulina had a curved tube, namely P. curvituba B. Pan, L.H. Yang & M. Kang (Yang et al. 2017), out of a total of about 210 species of Primulina in China (Wen et al. 2019, 2020).

Some studies have suggested that moss may play a positive role in affecting the survival and growth of some Primulina species, for instance P. tabacum Hance (Ren et al. 2010a, b). Hence, one of the authors (PT), as a bryologist, is also very concerned about the biodiversity of Primulina when he carries out the fieldwork for bryophyte biodiversity and flora. Significantly, when PT investigated bryophyta in Duyun City, southern Guizhou Province in the autumn of 2017, an unknown species of Gesneriaceae, but one without flowers, was collected. The vegetative characters of the individuals of this species, e.g. their small but conspicuous rhizome, opposite leaves, fleshy, and elliptical but fragile leaf blade, indicated that it should be classified as a member of Primulina. It is somewhat similar to P. tenuituba (W.T. Wang) Yin Z. Wang, namely former Deltocheilos tenuitubum W.T. Wang (Wang 1981a) and Chirita shennungjiaensis W.T. Wang (Wang 1981b; Wang et al. 1990) because of the leaf blade morphology and shape. Several living individuals were then introduced into the nursery and gardens at the Gesneriad Conservation Center of China (GCCC), at the Guilin Botanical Garden, Chinese Academy of Sciences. After six months, those introduced and cultivated plants blossomed in April 2018. To our surprise, the gross morphology of flowers, such as their curved corolla tube, was obviously different from all other species of Primulina, except for P. curvituba. We revisited the locality immediately to collect flowering plants in the field (Figure 1). Surprisingly, when we showed photographs to the staff of the Guangxi Institute of Botany, one of the authors (BP) told us that he had been collecting the flowering specimens and living plants of this species back in 2016. Further literature study (e.g. Wang et al. 1998; Li and Wang 2005; Wei et al. 2010 and all recent published papers for new taxa of Primulina) and morphological comparison convinced us that it represents a new species to science, which is described and illustrated below.

Figure 1. 

The flowering plants of Primulina flexusa growing in the crevice of limestone hill (type locality): A–D flowering plants from different aspects.

Taxonomic treatment

Primulina flexusa F. Wen, Tao Peng & B. Pan, sp. nov.

urn:lsid:ipni.org:names:77211381-1
Figures 1, 2

Type

China. Guizhou Province, Duyun City, Bamang town, Longtang village, 26.31N, 107.49E, altitude ca. 1040 m, 15 May 2016, Bo Pan et al., PB160425-01 (Holotype: IBK!; Isotype: IBK!).

Diagnosis

The new species resembles Primulina curvituba in having a curved corolla but is easily distinguished from the latter by bracts oblong (vs. lanceolate), filament glabrous (vs. glandular-pubescent), ovary ovoid (vs. cylindrical), stigma slightly 2-parted at the apex (vs. undivided at apex) and capsule ovoid (vs. linear).

Description

Herbs perennial, acaulescent. Leaves basal, 8–12, opposite, petiolate; petiole compressed, gradually broadened from the base to the upper, densely pilose, 5–13 × 1.5–3.5 mm; leaf blade ovate to broadly ovate, abaxial surface green to dark green, adaxial surface brownish-green to brownish-purple; 1.6–2.0 × 1.3–1.8 cm, pubescent and pilose on adaxial surface, puberulent on abaxial surface, base shallowly cordate to slightly cuneate, margin entire and ciliate, apex obtuse to nearly rounded; lateral veins ca. 3 on each side of the midrib, inconspicuous on adaxial surface, prominent on the abaxial surface. Cymes 2–4, 1–4-flowered; peduncle 1.5–2.4 cm long, ca. 1 mm in diameter, erect pubescent; bracts 2, opposite, oblong, ca. 3.8 × 0.7 mm, adaxially green and nearly glabrous, abaxially brownish-green to brownish-purple, densely pilose, the pilose hairs 0.8–1.2 mm long, margin entire, apex acute, bracteole ca. 2.4 × 0.5 mm, color and indumentum same as bracts. Pedicel 6.5–8 mm long, ca. 0.9 mm in diameter, puberulent. Calyx 5-parted from the base; segments equal, pale brown to brown, lanceolate, 4–5 × 0.7–0.9 mm, outside pale brown to greenish-brown, densely pubescent, inside greenish-brown, glabrous, margin entire, apex acute. Corolla 21–25 mm long, pale purple to purple, throat with two distinctly dark purple stripes respectively between each pair of abaxial lip lobes, outside covered with extremely short glandular-puberulent hairs, inside nearly glabrous; corolla tube infundibuliform, slightly curved downwards at base (ca. 4 mm from the base), then gradually bent forwards, 16–19 mm long, ca. 6 mm in diameter at the mouth, ca. 2.5 mm in diameter at the base; limb distinctly 2-lipped, adaxial lip 2-parted over 2/3 from the top of the adaxial lip, lobes nearly equal, broadly obovate, ca. 5 × 4 mm; abaxial lip 3-parted over 4/5 from the top of the abaxial lip, lobes slightly obliquely obovate, 7.5–8 × 3.9–5 mm. Stamens 2, adnate to ca 2.5 mm above the corolla base; anthers pale yellowish-brown, elliptic, ca. 1.5 × 1.0 mm, fused by entire adaxial surfaces; filaments linear, straight, ca. 3 mm long, white, glabrous; staminodes 3, adnate to ca. 3 mm above the corolla tube base, lateral ones ca. 3.5 mm long, the middle one ca. 0.7 mm long. Disc yellowish-green, annular, margin entire or sometimes slightly erose, ca. 0.4 mm high. Pistil ca. 5 mm long; ovary brownish-red, ovoid, ca. 1.4 mm long, ca. 0.9 mm in diameter, densely puberulent and glandular-puberulent; style white, 2.2–2.5 mm long, ca. 0.2 mm in diameter, sparsely glandular-puberulent. Stigma 1, translucent to white, its upper lobe lacking, lower lobe obtrapeziform, slightly 2-parted at apex, ca. 1 mm long, ca. 0.75 mm wide. Capsule ovoid, ca. 6.5 mm long, ca. 2.2 mm in diameter, densely puberulent.

Phenology

Flowering occurs from April and fruiting from May to June.

Etymology

The specific epithet ‘flexusa’ is derived from its curved corolla tube. The original epithet ‘flexusa’ derived from the Latin, ‘flexus’, means curved and slightly zigzagging.

Vernacular name

Qū Guǎn Bào Chūn Jù Tái (Chinese pronunciation); 曲管报春苣苔 (Chinese name).

Distribution and habitat

Primulina flexusa is hitherto only known from the type locality, Mangba town, Duyun City, Guizhou Province, Southwest China, growing on moist and shaded rocky crevice on the cliff in a subtropical evergreen seasonal rain forest, at an altitude of ca. 1040 m. All plants were growing in a damp and dark crevice of Karst cliff near a village.

Conservation status and IUCN RedList category

Only a single population with ca. 100 mature individuals is known to exist at the type locality. All individuals were found growing in a large horizontal crevice close to the hillside of the limestone hill. The hill is isolated by maize fields. We, therefore, assess Primulina flexusa as Critically Endangered (CR C1), according to IUCN RedList Categories and Criteria (IUCN 2019). The CR category assessment of this new species is based on the distributional range that extends ca. 5 km2 around the type locality at present, as observed in the past two years.

Additional specimens examined

Primulina curvituba B. Pan, L.H. Yang & M. Kang, China: Guangdong Province, Guangzhou City, cultivated in South China Botanical Garden, introduced from Guangxi Zhuangzu Autonomous Region, 25°11'31.83"N, 108°14'52.41"E, growing on the moist rock surfaces of limestone hills, 29 Jul 2016 (flowering), Li-Hua Yang, YLH368 (holotype: IBSC!). Primulina tenuituba (W.T. Wang) Y.Z. Wang, China: Hunan Province, Yongshun County, Qingtianping, growing on the limestone cliff, 14 April 2013, Hong-Wen Huang 40826 (CSFI!);Hunan Province, Longshan County, no detailed information, 11 April 2013, Dai-Ke Tian, Yan Xiao, Yue Chen LS-1310 (CSH!); Hunan Province, Suining County, Huangsang National Natural Reserve, Huangsang Village, Dawanpeng, 413 m a.s.l., 20 April 2014, Jian-Jun Zhou & Zong-Ping Song 1404145 (CSFI!); Hunan Province, Suining County, Huangsang National Natural Reserve, Pingxi Village, Banchong, 894 m a.s.l., 3 May 2014, Jian-Jun Zhou & Zong-Ping Song 1405039 (CSFI!); Hunan Province, Suining County, Huangsang National Natural Reserve, Chiban Village, Yuanyang, 461 m a.s.l., 7 April 2013, Jian-Jun Zhou & Dian Zhou 13024 (CSFI!); Hunan Province, Suining County, Huangsang National Natural Reserve, Dawantang Village, Da, 410 m a.s.l., 11 April 2013, Jian-Jun Zhou & Dian Zhou 13136 (CSFI!); Hunan Province, Suining County, Huangsang National Natural Reserve, Chiban Village, Yuanyang, 487 m a.s.l., 11 April 2013, Jian-Jun Zhou & Dian Zhou 13121 (CSFI!); Guizhou Province, Tongren City, Yangtou District, Jiulongdong, growing on the surface of rocks, 8 July 1988, Wulingshankaochadui 1577 (PE!); Guizhou Province, Guiyang City, Dongshan, growing in the crevices of limestone hill, 8 May 1991, De-Yuan Chen & Cheng-Gang Hu, s.n. (PE!); same locality, 21 May 1989, De-Yuan Chen, s.n. (PE!); Sichuan Province, Daxian County, Pingchang, Heishui, 600 m a.s.l., 1 June 1978, Pingchangdui 212 (SM!); Sichuan Province, Bazhong City, Daluo, Shedan, 700 m a.s.l., 8 March 1979, Bazhongpuchadui 879 (SM!); Sichuan Province, Dazhu County, Zhuqi, Sanqi, Zhongfeng, 9 September 1978, Dazhuxian 0803 (SM!); Sichuan Province, Nanjiang County, Yangba, 28 August 1978, 949 (SM!); Sichuan Province, Xiushan County (Chongqing City now), Shitang, 370 m a.s.l., 17 May 1979, 0349 (SM!).

Figure 2. 

Primulina flexusa sp. nov. A habitat B habitat and flowering plant for showing curved corolla tube C adaxial surfaces of leaves D abaxial surfaces of leaves E cultivated potted plant in flowering F cyme G adaxial surfaces of bract (right) and bracteole H lateral view of corolla for showing curved corolla tube I opened corolla J calyx lobes K pistil L stigma M mature capsule.

Notes

This new species is closely related to Primulina curvituba (Figure 3A), from which its vegetative and reproductive organs are obviously different, as stated in the diagnosis. The new species also resembles P. tenuituba; however, the latter has no curved corolla tube (Figure 3B). The detailed morphological differences among the three species are summarized in Table 1.

Table 1.
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Detailed comparisons among Primulina flexusa, P. curvituba, and P. tenuituba.

Characters P. flexusa P. curvituba P. tenuituba
Leaf blade
Shape ovate to broadly ovate elliptical to linear-elliptical ovate to suborbicular
Size 1.6–2.0 × 1.3–1.8 cm 1.4–3.3 × 0.9–1.5 cm 1–3.2 × 0.8–2.5 cm
Indumentum pubescent and pilose on abaxial surface, puberulent on the adaxial surface with both surfaces densely white pubescent appressed pubescent to appressed pilose
Margin entire and ciliate entire and revolute entire to repand-crenate
Cyme
Number / per plant 2–4 6–11 2–4
Peduncle length 1.5–2.4 cm 3–6.5 cm 0.6–1.4 cm
Bracts
Shape oblong lanceolate narrowly triangular to lanceolate
Size ca. 3.8 × 0.7 mm 2.0–3.5 × 1.0–1.5 mm 0.8–3 × 0.3–1 mm
Indumentum adaxially nearly glabrous, abaxially densely pilose adaxially glabrescent, abaxially densely white pubescent adaxially glabrescent, abaxially puberulent to pilose
Pedicel
Length 6.5–8 mm 20–30 mm 2–5.5 mm
Indumentum puberulent densely pubescent densely spreading puberulent to pilose
Calyx lobes size 4–5 × 0.7–0.9 mm 2–3 × 1.0–1.5 mm 4.5–5.5 × 0.8–1.2 mm
Corolla indumentum outside covered extremely short glandular-puberulent hairs, inside nearly glabrous outside pubescent, inside glabrescent outside sparsely puberulent, inside puberulent below the abaxial lip
Corolla tube infundibuliform, slightly curved downwards at the base (ca. 4 mm from the base), then gradually bent forwards infundibuliform, laterally compressed at the mouth, strongly curved downwards at the base (5 – 7 mm from the base), then bent forwards cylindric, straight
Filament
Length ca. 3 mm 5–6 mm 4.5–5.5 mm
Indumentum glabrous glandular-pubescent Glabrous
Staminodes number and length 3, lateral ones ca. 3.5 mm, the middle one ca. 0.7 mm 3, lateral ones 1–2 mm, middle one ca. 1 mm 2, 0.5–0.8 mm
Pistil
Length ca. 5 mm 7–8 mm 19–22 mm
Ovary
Length ca. 1.4 mm 5–6 mm 3.2–6 mm
Shape ovoid cylindrical Cylindrical
Stigma slightly 2-parted at apex undivided at apex 2-parted at apex
Capsule
Length ca. 6.5 mm 10–15 mm 2–2.8 mm
Shape ovoid linear
Figure 3. 

A Primulina curvituba B P. tenuituba: 1 cultivated plants in flowering 2 frontal view of corolla 3 lateral view of corolla for showing the curved and straight corolla tube.

Acknowledgments

We thank Prof. Michael LoFurno from Temple University, Philadelphia, U.S.A., for his editorial assistance. This study was financially supported by the Foundation of Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain (19-050-6), the Guangxi Natural Science Foundation (2017GXNSFAA198006), the National Natural Science Foundation (31860047), Basal Research Fund of GXIB (Guizhiye20009) and 21st Talent project of “Ten-Hundred-Thousand” in Guangxi.

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