Petrocosmea weiyigangii (Gesneriaceae), a new species from a limestone cave in southern China

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Petrocosmea weiyigangii (Gesneriaceae), a new species
from a limestone cave in southern China
F. Wen
Guangxi Key Laboratory of Plant Conservation and Restoration Ecology
in Karst Terrain, Guilin Botanical Garden, Guangxi Institute of Botany,
Guangxi Zhuang Autonomous Region and the Chinese Academy of
Sciences, CN-541006, Guilin, Guangxi, China
wenfang760608@139.com
Gesneriad Conservation Center of China (GCCC),
CN-541006, Guilin, Guangxi, China
ABSTRACT. A new species, Petrocosmea weiyigangii F.Wen (Gesneriaceae), is described
from southern China. It differs from all other species of Petrocosmea in its deeply lobed leaf
blades. It is only known from a limestone cave in northwestern Guangxi, China. Following
the IUCN Red List categories and criteria, Petrocosmea weiyigangii is assessed as Critically
Endangered.
Keywords. Cave-dwelling plant, Gesneriad, Guangxi, IUCN conservation assessments,
limestone ora, new taxa, Petrocosmea martini
Introduction
When Dr Li-Bing Zhang from Missouri Botanical Garden, USA and Prof. Hai He
from Chongqing Normal University, China carried out a project on cave-dwelling
Polystichum Roth species in October 2010, they found a distinctive species of
Gesneriaceae in a large cave from Tianlin County, Guangxi, China. In this plant the
leaf blades are lobed for half or more of the width of each side of the blade to the
midrib, but not all the way to the midrib. The collectors sent me photos of this plant
nearly three years later and I was unable to identify it. In the intervening period, a new
species of Primulina Hance, P. multida B.Pan & K.F.Chung (Xu et al., 2012), which
has a pinnatid leaf blade margin, was published. The leaves of the unknown species
from Tianlin County (Fig. 1A) look rather like those of Primulina multida (Fig. 1B),
leading me to suspect that it may belong to Primulina at that time. In the years that
followed, I visited Langping Town, Tianlin County many times but without being
able to nd the cave and this interesting plant. Fortunately, during a eld investigation
of the limestone ora of Guangxi, China in May 2018, I accidentally found the cave
and the distinctive and attractive diminutive plant with deeply lobed leaves. Luckily
it was owering and the owers more resembled Petrocosmea Oliv. than Primulina.
I was unable to match it to any previously described species of Petrocosmea in the
Gesneriaceae collections from Guangxi, Yunnan, Guizhou, Xizang and Sichuan in
the principal herbaria in the region (e.g. GXMI, HITBC, IBK, IBSC, KUN, PE). I
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Gardens’ Bulletin Singapore 71 (1): 175–183. 2019
doi: 10.26492/gbs71(1).2019-11

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was also unable to match it to any described species of Petrocosmea on comparison
to images of specimens available in virtual herbaria (e.g. A, E, K, MO, P), and to
descriptions in local oras (Wang et al., 1990, 1998) and monographs (Li & Wang,
2004; Wei et al., 2010; Qiu et al., 2015a).
Petrocosmea belongs to subtribe Didymocarpinae, tribe Trichosporeae,
subfamily Didymocarpoideae of the Gesneriaceae (Weber et al., 2013). The genus
currently comprises 47 species in South, East and Southeast Asia (Möller et al., 2016;
Qiu et al., 2015a; Wei at al., 2010; Wang et al., 1990, 1998). Almost all Petrocosmea
species are found in damp habitats in limestone areas, except P. melanophthalma Huan
C.Wang et al. (Wang et al., 2013), P. begoniifolia C.Y.Wu ex H.W.Li (Li, 1983, Qiu
et al., 2015a), P. chrysotricha M.Q.Han et al. (Han et al., 2018) and P. sinensis Oliv.
(Oliver, 1887; Wei et al., 2010; Qiu et al., 2015a), which grow on damp surfaces and
in crevices of marble and sandstone rocks and cliffs. All hitherto known species of
Petrocosmea have leaf margins that are entire to serrate. The pinnatid leaf blade
margin of this new taxon is the most distinctive feature to distinguish it from other
species of Petrocosmea.
The new species is described and illustrated below. A provisional IUCN
conservation assessment following the guidelines by the IUCN Standards and
Petitions Subcommittee (2017) is also provided.
New species
Petrocosmea weiyigangii F.Wen, sp. nov.
The deeply lobed margin of the leaf blade distinguishes Petrocosmea weiyigangii
F.Wen from all other species of Petrocosmea. – TYPE: China, Guangxi Zhuangzu
Autonomous, Tianlin County, Langping town, 24°31’N, 106°19’E, alt. 1330 m, 18
May 2018, owering, Wei Yi-Gang & Wen Fang WYG180518-21 (holotype IBK;
isotype IBK, KUN). (Fig. 1A, 2–3)
Fig. 1. The similar leaf morphology of A. Petrocosmea weiyigangii F.Wen. and B. Primulina
multida B.Pan & K.F.Chung. (Photos: F. Wen).

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Petrocosmea weiyigangii, a new Gesneriad from southern China
Fig. 2. Petrocosmea weiyigangii F.Wen. A. Habitat. B. Habit, with author’s nger for scale.
C. Relative size of the adult plant with author’s hand for scale. D. Colony of owering plants.
E. Corolla viewed from the front. (Photos: F. Wen).
Perennial, stemless, rosulate herb. Rhizome extremely short, inconspicuous. Leaves
inconspicuously spiral, 21 to 30 per plant, petioles subterete, 20–45 mm long,
0.8–1 mm in diam., brown, densely puberulent; leaf blades herbaceous when dried,
ovate to rounded, slightly asymmetric to symmetric, 12–15 × 10–12.5 mm, base
cordate and truncate, margin deeply lobed, lobes 2–3 on each side of blade, each lobe
narrowly oblong to oblong, apices obtuse to nearly rounded, 2–3-veined, adaxially
and abaxially glabrous. Inorescences axillary, cymes usually 1-owered; peduncle
35–50 mm long, densely eglandular-pubescent to pilose; bracts 2, free and opposite,
ensiform, 2–3 mm long but usually caducous or withered before anthesis; pedicels
6–10 mm long, pubescent. Calyx nearly actinomorphic, equally divided into 5 lobes,
with outer surface sparsely pubescent and inner surface nearly glabrous; lobes equal,
broadly lanceolate, 6.5–8 × 3.5–5 mm, margin entire, apex acute. Corolla purple,
throat white, sparsely pubescent outside, glabrous inside; tube c. 9 mm long; adaxial

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178
lip c. 6.5 mm long, indistinctly 2-lobed with the two small lobes fused for almost
their entire length and each lobe folded and rolled laterally to form a carinate-plicate
(galeate) structure that encloses the style; abaxial lip c. 19 mm long, 3-lobed to the
middle, with oblong to semicircular lobes. Stamens 2, c. 10 mm long, adnate to the
base of the corolla tube; laments c. 6 mm long, geniculate near the middle with an
angle of about 150°, white pilose from the base to the middle; anthers ovate, c. 3.6
mm long, poricidal, glabrous, dorsixed, coherent at apex; staminodes 3, adnate to
the corolla tube at the base, glabrous. Disc greenish yellow, annular, glabrous, c. 1.5
mm high. Pistil c. 16 mm long; ovary densely white villous, ovoid, c. 5.5 mm long;
style semitransparent to white, c. 10.5 mm long; stigma punctiform, white. Capsules
straight in relation to pedicel, brown, long ellipsoid, 5–6 mm long, both loculicidally
and septicidally dehiscent.
Fig. 3. Petrocosmea weiyigangii F.Wen. A. A variety of leaves. B. Flower viewed from the top.
C. Abaxial surfaces of calyx lobes. D. Calyx lobes, adaxial surfaces. E. Corolla , opened up
to show stamens and staminodes. F. Pistil (Style, ovary and disc). G. Stamens with glabrous
anthers and white pilose laments. H. Mature dehisced capsule. (Photos: F. Wen).

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Petrocosmea weiyigangii, a new Gesneriad from southern China
Distribution. Only known from the type locality, a large limestone cave, near Tiandong
Village, Langping town, Tianlin County, Baise City, Guangxi Zhuangzu Autonomous
Region, China (Fig. 2A).
Habitat. The new species is only known from a very small area in the northwestern
part of Guangxi, where it has been collected on two occasions growing on damp rock
surfaces and in crevices at the bottom of a cliff in a large cave located between 1310
m and 1330 m above sea level. Petrocosmea weiyigangii appears to be restricted to
shady and damp limestone crevices in near-vertical, moss-covered tufa habitats in the
cave (Fig. 1A). The top of cliff above the cave mouth is covered in bushes and trees
(Fig. 2A), a similar habitat to many species of Primulina and Petrocosmea martini
(Fig. 4).
Etymology. The epithet ‘weiyigangii’ is coined in honour of the Chinese botanist
Prof. Yi-Gang Wei who has discovered, collected and described many new taxa of
Gesneriaceae and has contributed much to the study of plant diversity and ora in
Guangxi.
Fig. 4. Petrocosmea martini (H.Lév.) H.Lév. A. Habitat. B. Habit, with author’s nger for
scale. C. Plant in ower. D. Corolla viewed from the front. (Photos: F. Wen).

Gard. Bull. Singapore 71 (1) 2019
180
Vernacular names. 毅刚石蝴蝶. The Chinese pronunciation of Petrocosmea
weiyigangii is ‘Yì Gāng Shí Hú Dié’.
Provisional IUCN conservation assessment. Based on available information, the
extent of occurrence (EOO) and area of occurrence (AOO) of Petrocosmea
weiyigangii are both estimated at less than 4 km2. The entire population is only known
from a single cave which is not in a protected area. This area is subject to human
pressure, especially from deforestation and the grazing of goats and cattle. Even if the
exact location of the plants is not under direct threat, these local vegetation changes
will alter the micro-climate and ecological conditions, thereby impacting humidity
and shade and altering the specialised habitat of Petrocosmea weiyigangii. This results
in a projected continuing decline in both habitat quality and the number of mature
individuals (IUCN Standards and Petitions Subcommittee, 2017). I therefore propose
that Petrocosmea weiyigangii should be provisionally assessed as Critically
Endangered CR B1ab(iii,v), B2ab(iii,v).
Notes. When this new taxon was rst discovered by Dr Zhang and Prof. He, none
of the plants were in ower, leading me to suspect it was a Primulina from the
photos they sent me. When I observed its owers and fruits in the eld I discovered
it possessed a number of characters typical of Petrocosmea: corolla tube broadly
tubular and shorter than limb; laments inserted at base of corolla; no disc; stigma
capitate; capsule straight in relation to pedicel, narrowly ellipsoid to oblong to ovoid,
nearly as long as calyx, dehiscing loculicidally to base, valves 2, straight, not twisted.
Petrocosmea was previously divided into three sections, namely Petrocosmea sect.
Petrocosmea Craib, Petrocosmea sect. Anisochilus Hemsl. and Petrocosmea sect.
Deinanthera W.T.Wang (Wang, 1985). Now this genus has been restructured into ve
sections: those above plus Petrocosmea sect. Minor Z.J.Qiu and Petrocosmea sect.
Barbatae Z.J.Qiu based on morphological and molecular evidence (Qiu et al., 2011,
2015a, 2015b). The characters of Petrocosmea sect. Anisochilus include not having
constricted anthers, an actinomorphic calyx divided into ve segments and the calyx
lobe margins entire. There are not many species of Petrocosmea in Guangxi: only P.
forrestii Craib., P. iodioides Hemsl., P. martini (H.Lév.) H.Lév. and P. minor Hemsl.
have previously been recorded. Of all species found in Guangxi, Petrocosmea martini
(Fig. 4) is clearly the most similar to P. weiyigangii (Table 1). They have a similar
oral structure: notably, the upper lip is conspicuously galeate and is about half the
length of the lower lip. The owers of the two species differ in corolla size with the
corolla of Petrocosmea weiyigangii larger than P. martini (tube c. 9 mm long, adaxial
lip c. 6.5 mm long and abaxial lip c. 19 mm long in P. weiyigangii vs. tube c. 3 mm
long, adaxial lip c. 3 mm long and abaxial lip c. 6.5 mm long). These oral characters
suggest that P. weiyigangii belongs to Petrocosmea sect. Anisochilus ser. Iodioides
W.T.Wang. Unlike Petrocosmea weiyigangii, P. martini (Fig. 4) is widely distributed
on the Yunnan-Guizhou Plateau (including Guizhou and Yunnan provinces and

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Petrocosmea weiyigangii, a new Gesneriad from southern China
Table 1. Morphological comparison of Petrocosmea weiyigangii and P. martini.
Characters P. weiyigangii P. martini
1. Leaf blade a. Shape Ovate to rounded Ovate to orbicular-ovate
b. Margin Deeply 2–3-lobed on
each side of blade, each
lobe narrowly oblong to
oblong
Crenulate to denticulate,
not lobed
c. Indumentum Adaxially and abaxially
glabrous
Adaxially pilose,
abaxially densely pilose
2. Calyx lobe shape and size Broadly lanceolate,
6.5–8 × 3.5–5 mm
Narrowly lanceolate,
2.5–3 × 0.8–1.5 mm
3. Filament length and
indumentum
c. 6 mm long, white
pilose from the base to
the middle
2–3 mm long, rusty-
brown puberulent or
glabrous
4. Staminode number 3 2
5. Pistil length c. 16 mm long 6–8 mm long
6. Style length c. 10.5 mm long 1.5–2 mm long
northwestern Guangxi). The distribution of Petrocosmea weiyigangii is entirely within
the range of distribution of P. martini (Fig. 5) and they are likely to be closely related
with the unique morphological features of the former due to adaptation to its special
cave environment or by the long geological isolation (Monro et al., 2018; Tao et al.,
2015).
ACKNOWLEDGEMENTS. I thank Stephen Maciejewski and Dr David J. Middleton
for checking the manuscript, and Dr. Li-Bing Zhang from Missouri Botanical Garden,
U.S.A. and Prof. Hai He from Chongqing Normal University, China for providing useful
information on this species and the cave. This study was nancially supported by the Guangxi Key
Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain (17-259-23);
the Natural Science Foundation of Guangxi (2017GXNSFAA198006); Guangxi science and
technology project (Guike AB16380053); the STS Programme of the Chinese Academy of
Sciences (KFJ-3W-No1); Science Research Foundation of Guangxi Academy of Sciences
(2017YJJ23022); and the National Natural Science Foundation of China (31460159 &
31860047).

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182
Fig. 5. Distribution of Petrocosmea weiyigangii F. Wen (★), marked as ‘B’, and its relative,
P. martini (H.Lév.) H.Lév. (in the elliptical area, marked as ‘A’) in China.
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