Research Article
Research Article
A new combination and a new synonym of Gesneriaceae in China
expand article infoZheng-Long Li§, Zhang-Jie Huang|, Da-Wei Chen, Xin Hong#, Fang Wen§
‡ Anhui University, Hefei, China
§ Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences, Guilin, China
| Northwest University, Xi'an, China
¶ Guilin Botanical Garden, Chinese Academy of Science, Guilin, China
# Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
Open Access


Didymocarpus subpalmatinervis W.T.Wang was shown to be conspecific with Petrocodon lithophilus Y.M.Shui, W.H.Chen & Mich.Möller, by checking original literature, examining specimens, tracing specimen collecting history, and conducting field surveys. The results show morphological characteristics and geographical distribution overlaps between these two species. The transfer of Didymocarpus subpalmatinervis to Petrocodon as a new combination with Petrocodon subpalmatinervis (W.T.Wang) F.Wen & Z.L.Li is proposed here, and P. lithophilus is synonymized with P. subpalmatinervis. Color photographs and essential information are also provided, including a detailed comparison of description, distribution, habitat, and the proposed IUCN conservation status.

Key words

Didymocarpus, Flora of China, Gesneriaceae, new combination, new synonym, Petrocodon, taxonomy


Didymocarpus Wall. has a complex taxonomic history, saturated with doubtful taxa (Weber and Burtt 1998). Originally, in the taxonomic system of Burtt and Wiehler (1995), it was the largest genus in the tribe Didymocarpeae Endl., subfam. Cyrtandroideae, with more than 180 species. Weber and Burtt (1998) excluded the section Heteroboea, which was considered as part of Didymocarpus s. l (Hilliard and Burtt 1995; Weber and Burtt 1998). In addition, they considered that 1) D. hancei Hemsl. (endemic to China) and D. bonii Pellegr. (distributed in Vietnam and East Thailand) should be included in Calcareoboea C.Y.Wu ex H.W.Li, as well as D. mollifolius W.T,Wang and D. niveolanosus D.Fang & W.T.Wang; 2) D. demissus Hance should be assigned to the previous genus, Chirita Buch.-Ham. ex D. Don (Wei et al. 2010; Wang et al. 2011; Weber et al. 2011). Their notion of separating D. hancei from Didymocarpus Wall. was supported by Li (2007) based on morphological and molecular evidence. Weber et al. (2011) published three new combinations in their revision of the genus Petrocodon Hance, viz., Petrocodon hancei (Hemsl.) A.Weber & Mich.Möller (≡Didymocarpus hancei Hemsl.), Petrcodon mollifolius (W.T.Wang) A.Weber & Mich.Möller (≡Didymocarpus mollifolius W.T.Wang) and Petrocodon niveolanosus (D.Fang & W.T.Wang) A.Weber & Mich.Möller (≡Didymocarpus niveolanosus D.Fang & W.T.Wang). D. subpalmatinervis W.T.Wang, a species with no collection record after 1905, also has morphological characteristics placing it in section Heteroboea. The taxonomic status of this species remained unchanged because of the difficulty in obtaining type materials. Its problematic taxonomic status has previously been recognized by (Li et al. 2015; Möller et al. 2016; Hong et al. 2018).

The French Catholic priest Francois Ducloux (1864–1945), the head of the Kunming Church from 1889 to 1945, hired people to collect plant specimens extensively in central and northern Yunnan (Qu 2014). In 1905, Ducloux collected a Gesneriaceae-like taxon, perennial and acaulescent in Y-dje, near Lou-lan, Yunnan, China (collection number Fr. Ducloux 3711). He sent three sheets back to the Museum of Natural History in Paris. Since then, those specimens were neglected in P for over 90 years, until in 1996, Wen-Tsai Wang identified Ducloux’s specimens as a new species belonging to Didymocarpus sect. Heteroboea and published it as Didymocarpus subpalmatinervis subsequently a year later (Weitzman et al. 1997).

Petrocodon lithophilus was described at the morphological and molecular level from Naigu Stone Forest, Yunnan Province, where Michael Möller and Yu-Min Shui first discovered it in August 2012. It is placed in Petrocodon by some obvious characters of this genus, viz. a rhizomatous rosette with leaves usually rounded or elliptic, mainly in an alternate arrangement, filaments straight, stigma discoid, and fruits dehiscing loculicidally into two valves (Chen et al. 2014).

When sorting out the specimens of Didymocarpus sect. Heteroboea of, the type specimen of D. subpalmatinervis (Fr. Ducloux 3711), morphologically, was found to be extremely similar to Petrocodon lithophilus. According to protologue and label information on the type specimen, the type locality of Didymocarpus subpalmatinervis is near Lunan Stone Forest, only 13 kilometers away from Naigu Stone Forest. During field investigations near the type locality of Petrocodon lithophilus, several populations of Didymocarpus aff. subpalmatinervis were also found on the hills. The authors concluded that D. subpalmatinervis is conspecific with Petrocodon lithophilus. Accordingly, it is reasonable to make a new combination P. subpalmatinervis, and reduce P. lithophilus to a synonym.

Materials and methods

A thorough comparison of the type material of Petrocodon lithophilus and Didymocarpus subpalmatinervis was made. Their protologues and relevant records were studied intensively. The geographical distribution of the two species was outlined by careful field surveys of the type locality areas. Classical plant taxonomic methods were involved. Major online herbarium databases, including P (, E (, K (, A (, PE ( and Chinese Virtual Herbarium (, et al., were checked. The only recorded specimens of D. subpalmatinervis stored at P were affirmed and checked, utilizing high-resolution digital images of the type specimen. In addition, the authors observed and recorded morphological characters of Petrocodon lithophilus in the field and examined its type specimen at KUN.


Comparison and discussion of morphological characteristics of sect. Heteroboea

There are numerous distinct morphological characteristics distinguishing Didymocarpus subpalmatinervis from other species within sect. Heteroboea, such as leaves’ margins obtusely or doubly dentate (vs. margin irregularly triangular denticulate), triangular lobes (vs. rounded or oblong lobes), straight filaments (vs. curving), separate anthers (vs. confluent anthers). Detailed morphological comparisons with sect. Heteroboea are provided in Fig. 1. Based on the aforementioned, it becomes evident that D. subpalmatinervis is not a species within sect. Heteroboea. Additionally, owing to its stemless habit, it does not align with sect. Didymocarpus either. Consequently, the taxonomic classification of this species falls outside the scope of the Didymocarpus genus. Given its overall vegetative traits, it should be reclassified under the genus Petrocodon.

Figure 1. 

Morphological comparisons of Didymocarpus subpalmatinervis and sect. Heteroboea A type specimen of D. subpalmatinervis B habit of D. heucherifolius var. yinzhengii C habit of D. cortusifolius D habit of D. yuenlingensis E habit of D. heucherifolius var. gamosepalus F leaves of D. subpalmatinervis G leaves of D. heucherifolius var. yinzhengii H leaves of D. lobulatus I leaves of D. heucherifolius J opened corolla of D. subpalmatinervis, showing lobes and stamens K frontal view of D. yuenlingensis, showing lobes and stamens L frontal view of D. cortusifolius, showing lobes and stamens M frontal view of D. sinoprimulinus, showing lobes and stamens.

Comparison and discussion of morphological description with Petrocodon lithophilus

Comparing the description of Didymocarpus subpalmatinervis and Petrocodon lithophilus in their protologues, we found consistency in habit, leaves, calyx, corolla, disc, and ovary (indicated by “●” in Table 1). Because Wen-Tsai Wang described D. subpalmatinervis (Weitzman et al. 1997) according to the over 90-year-old type specimen, there may be some distortion compared with wild-living plants in morphology. Moreover, terminology may alter to a certain degree among different taxonomists due to personal preference in the use of words. Taxonomic descriptions have evolved over the years, as have identification tools. For example, Wang selected ‘puberulous’ and Shui picked up ‘pubescent’ to describe the hair of Didymocarpus subpalmatinervis and Petrocodon lithophilus, respectively. Such equivalents used by them in the description are marked with “★” in Table 1. The only significant difference appeared in the statement of staminode’s number: 2 in Didymocarpus subpalmatinervis and 3 in Petrocodon lithophilus (indicated by “▲” in Table 1). This feature has already been questioned by Wen et al. (2020). Previous researchers often made mistakes in describing the number of staminodes because 1) they followed generic diagnoses of Didymocarpus and paid no attention to the actual stamineal condition; 2) staminodes are inconspicuous in many species unless they are carefully observed, but the correct number of staminodes is 3. Detailed morphological comparisons with P. lithophilus are provided in Fig. 2.

Table 1.

The description and comparison of the D. subpalmatinervis and P. lithophilus.

Didymocarpus subpalmatinervis W.T.Wang Petrocodon lithophilus Y.M.Shui, W.H.Chen & Mich.Möller The similarity in description between the two species
Habit Perennial, stemless herb Perennial herbs
Leaves shape leaf blade ovate to oblate leaf blade rounded or elliptic
hair adaxially densely appressed puberulous, abaxially appressed puberulous, pilose on veins pubescent on both surfaces
base cordate nearly cordate
margin obtusely or doubly dentate shallowly or deeply crenulate
apex obtuse rounded
Cymes number Cymes ca. 2, ca. 2× branched, 2–10–flowered; about10 flowers
peduncle puberulous pubescent
bracts 2–3, narrowly lanceolate or linear, puberulous 2, linear or lanceolate, pubescent
Calyx Calyx actinomorphic, 5-sect or nearly so, segments linear-triangular, both surfaces puberulous Calyx 5-lobed to base, segments linear, pubescent
Corolla color Yellow light greenish-yellow
length 2–2.5 cm 2.5–2.8 cm
tube funnelform-cylindric, 1.4–1.7 cm thin tubular, 1.7–1.9 cm
lobes upper lip 2-lobed, lower lip 3-lobed, all lobes triangular adaxial lip 2-lobed, lobes triangular, abaxial lip 3-lobed, lobes triangular
Stamens staminodes 2 3
Disc annular ring-like
Pistil ovary ovary linear ovary linear inflated
hairs puberulous pubescent
stigma depressed capitate stigma 1, disc-like and undivided
Figure 2. 

Morphological comparison of Didymocarpus subpalmatinervis and Petrocodon lithophilus A–C, F1–I1: D. subpalmatinervis D, E, J, F2–I2: P. lithophilus A holotype P04060419 B isotype P04060165 C isotype P04060418 D holotype KUN-1519980 E Isotype KUN-1519978 F flower G abaxial surface of Leaves H adaxial surface of Leaves I opened corolla J staminodes.

The similarity in protologues prompts us to reconsider the circumscription of Didymocarpus subpalmatinervis and Petrocodon lithophilus.


In 1905, Ducoux collected Didymocarpus subpalmatinervis at the position of Y-dje, near Lou-lan. Lou-lan is the French pronunciation of 路南 (Lùnán) in Chinese, and Y-dje corresponds to 维则 (Wéizé). The scope of Lou-lan is not indicated on the type specimens of D. subpalmatinervis. China in 1905 was still in the era of the Qing Dynasty. Lunan then refers to Lunanzhou, which is now Shilin County. Naigu Stone Forest is included in Lunan County (now Shilin County). Lunan refers to Lunan Stone Forest. Lunan Stone Forest and Naigu Stone Forest are both in the Stone Forest scenic spot today. Our field survey shows only one species of Gesneriaceae with similar morphological characteristics in these two regions. The distribution of the two species thus overlaps no matter which geographical entity Lunan refers to in the past or present.

In summary, based on literature research, geographical distribution, and morphological analysis, we find no discontinuities and recognize Didymocarpus subpalmatinervis and Petrocodon lithophilus as conspecific. Therefore, a new combination, P. subpalmatinervis (W.T.Wang) F.Wen & Z.L.Li, comb. nov. is proposed here.

Taxonomic treatment

Petrocodon subpalmatinervis (W.T.Wang) F.Wen & Z.L.Li, comb. nov.

Didymocarpus subpalmatinervis W.T.Wang, Novon 7(4): 428–429. 1997. Type: China. Yunnan: Y-dje, near Lou-lan, July 1905, Fr. Ducloux 3711 (P: holotype P04060419!; isotypes P04060165!, P04060418!). Basionym.

= Petrocodon lithophilus Y.M.Shui, W.H.Chen & Mich.Möller, Sys. Bot. 39(1): 325. 2014. syn. nov. Type: China. Yunnan: Shilin County, Naigu Stone Forest, alt. 1848 m, on rocks on cliffs, 29 August 2012, Y.M. Shui et al. B2012–078 (KUN: holotype KUN-1519980!; isotype KUN-1519978!).

Chinese Vernacular name

掌脉石山苣苔 (Zhǎng Mài Shí Shān Jù Tái).

Distribution and habitat

This species is endemic to Shilin County, Yunnan Province, China, growing in narrow cracks on rocks. Accompanying plants include other shade herbs and trees.

Proposed IUCN conservation status

Naigu Stone Forest is a famous scenic spot for many tourists. The population of Petrocodon subpalmatinervis is easily affected by human activities. For example, tourists probably collect the conspicuous flowers of P. subpalmatinervis while they visit the scenic spot and walk along the trails among the Karst peaks and hills of Naigu Shilin. As mature individuals are easily damaged, the population will likely gradually decline year by year. According to the results of our field investigation in the type locality and adjacent regions, the EOO and AOO of P. subpalmatinervis are about 800 km2 and 30 km2. Despite the severe drought in the second half of 2022 seriously influencing the plant population, there is still a high number of individuals (more than 5 000) surviving in the scenic spot. In addition, authors also found several small populations (total>1 000) in the Karst landscape surrounding the type locality, Naigu Shilin. Following the IUCN Red List Categories and Criteria (IUCN 2022), this species is evaluated as Endangered [EN B1ab (i, ii, iii, iv)+2ab (i, ii, iii, iv)].


When Wang published the protologue of Didymocarpus subpalmatinervis, the collection date read 1909. But, on the website of CVH and the herbarium P, the collection date of the information of the specimen we consulted was 1905. Their two different collection years are confusing. We carefully compared the labels of three type specimens of D. subpalmatinervis with the collection number ‘3711’ and found that the collector’s writing habits might have caused this misunderstanding. Ducloux’s personal collection number increased with time like many collectors. For example, the collection number of Berberis bodinieri H.Lév. he collected in 1896 was ‘0004’; in 1904, the collection number of Potamogeton distinctus A. Benn. was ‘2571’; in 1905, he collected Cornus capitata Wall. at the same place (Y-dje near Lou-lan) with the collection number ‘3715’; In 1909, the collection number of Merremia yunnanensis (Courchet & Gagnep.) R.C.Fang has reached ‘6398’. Therefore, it seems likely that the specimens of D. subpalmatinervis with the collection number Fr. Ducloux 3711 were collected in 1905.

For some species published decades or even a hundred years ago, obtaining molecular materials for systematic analysis is challenging because there may be only one type specimen or a few specimens, or they are stored in a foreign herbarium (Wei 2018; Kong et al. 2021). Despite this complicated background, it is still reasonable and accurate to conduct an analysis and verification of the type specimen of the dubious species. When combined with the collecting history of the Ducloux, and the current situation of the existing population (Wei et al. 2022), we are confident about the name and status.


The authors are grateful to Mr. Zhen-Hao Feng for his generous support and Dr. Su Liu for his translation of the toponym. We also want to thank Stephen Maciejewski, the Gesneriad Society, and Michael LoFurno, Associate Professor, Temple University, Philadelphia, USA, for their editorial assistance. We are grateful to Bing Liu for his suggestions on taxonomy, University of Chinese Academy of Sciences.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.


This study was financially supported by the Key Science & Technology Research and Development Project of Guangxi (Guike AD20159091 & ZY21195050), the Basic Research Fund of Guangxi Academy of Sciences (grant no.CQZ-C-1901), the capacity-building project of SBR, CAS (KFJ-BRP-017-68), the Fund of Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations (PSESP2021F07).

Author contributions

ZL, ZH and DC inspected the specimens of the species. ZL, FW, and ZH performed the data analysis. ZL and ZH wrote the manuscript. FW and XH revised the manuscript. All authors have read and approved the final manuscript.

Author ORCIDs

Zheng-Long Li

Zhang-Jie Huang

Da-Wei Chen

Xin Hong

Fang Wen

Data availability

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


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