$¢PhytoKeys PhytoKeys 232: 99-107 (2023) DOI: 10.3897/phytokeys.232.108644 Research Article A new combination and a new synonym of Gesneriaceae in China Zheng-Long Li'?®, Zhang-Jie Huang*®, Da-Wei Chen'®, Xin Hong'*5®, Fang Wen?4© 1 Anhui Provincial Engineering Laboratory of Wetland Ecosystem Protection and Restoration, School of Resources and Environmental Engineering, Anhui University, CN-230601, Hefei City, Anhui Province, China 2 Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, Guangxi Institute of Botany, Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences, CN-541006, Guilin City, Guangxi Zhuang Autonomous Region, China 3 Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, CN-710069, Xi’an, Shaanxi Province, China 4 Gesneriad Committee of China Wild Plant Conservation Association, National Gesneriaceae Germplasm Resources Bank of GXIB, The Gesneriad Conservation Center of China, Guilin Botanical Garden, Chinese Academy of Sciences, CN-541006 Guilin, Guangxi, China 5 Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, CN-650201, Kunming, Yunnan, China Corresponding authors: Xin Hong (hongxin1989@vip.qq.com); Fang Wen (wenfang760608@139.com) OPEN Qaceess Academic editor: Alan Paton Received: 26 June 2023 Accepted: 24 August 2023 Published: 15 September 2023 Citation: Li Z-L, Huang Z-J, Chen D-W, Hong X, Wen F (2023) A new combination and a new synonym of Gesneriaceae in China. PhytoKeys 232: 99-107. https://doi.org/10.3897/ phytokeys.232.108644 Copyright: © Zheng-Long Li et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International - CC BY 4.0). Abstract Didymocarpus subpalmatinervis W.T.Wang was shown to be conspecific with Petroco- don lithophilus Y.M.Shui, W.H.Chen & Mich.Moller, by checking original literature, exam- ining specimens, tracing specimen collecting history, and conducting field surveys. The results show morphological characteristics and geographical distribution overlaps be- tween 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 photo- graphs 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 syn- onym, Petrocodon, taxonomy Introduction Didymocarpus Wall. has a complex taxonomic history, saturated with doubt- ful 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 Didymo- carpus s. | (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. * These authors contributed equally to this work. 99 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China 2011). Their notion of separating D. hancei from Didymocarpus Wall. was sup- ported 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.Moller (=Didymocarpus hancei Hemsl.), Petrcodon mollifolius (W.T.Wang) A.Weber & Mich.Moller (=Didymocarpus mollifolius W.T.Wang) and Petrocodon niveolano- sus (D.Fang & W.T.Wang) A.Weber & Mich.Mo6ller (=Didymocarpus niveolanosus D.Fang & W.T.Wang). D. subpalmatinervis W.T.Wang, a species with no collec- tion record after 1905, also has morphological characteristics placing it in sec- tion 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; M6ller 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 col- lected a Gesneriaceae-like taxon, perennial and acaulescent in Y-dje, near Lou- lan, Yunnan, China (collection number Fr. Ducloux 3717). 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. Het- eroboea 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 Moller 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, stig- ma 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), morphological- ly, 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 kilome- ters 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 Didy- mocarpus 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 tax- onomic methods were involved. Major online herbarium databases, includ- ing P (https://science.mnhn.fr/institution/mnhn/search), E (http://www.rbge. PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 100 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China org.uk/), K (https://www.kew.org/), A (https://huh.harvard.edu/), PE (https:// pe.ibcas.ac.cn/index.html) and Chinese Virtual Herbarium (https://www.cvh. ac.cn/), et al., were checked. The only recorded specimens of D. subpalmat- inervis 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. Results 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 tri- angular denticulate), triangular lobes (vs. rounded or oblong lobes), straight filaments (vs. curving), separate anthers (vs. confluent anthers). Detailed mor- phological 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 taxonom- ic 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. Comparison and discussion of morphological description with Petrocodon lithophilus Comparing the description of Didymocarpus subpalmatinervis and Petroco- don lithophilus in their protologues, we found consistency in habit, leaves, calyx, corolla, disc, and ovary (indicated by “e” 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 identifi- cation tools. For example, Wang selected ‘puberulous’ and Shui picked up ‘pu- bescent’ to describe the hair of Didymocarpus subpalmatinervis and Petroco- don 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 “A” in Table 1). This feature has already been questioned by Wen et al. (2020). Previous researchers often made mis- takes in describing the number of staminodes because 1) they followed gener- ic 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 mor- phological comparisons with P lithophilus are provided in Fig. 2. PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 101 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China \ iin \ 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 | leaves of D. heucherifolius J opened corolla of D. subpalmatinervis, showing lobes and stamens K fron- tal 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. The similarity in protologues prompts us to reconsider the circumscription of Didymocarpus subpalmatinervis and Petrocodon lithophilus. Locality In 1905, Ducoux collected Didymocarpus subpalmatinervis at the position of Y-dje, near Lou-lan. Lou-lan is the French pronunciation of #& Fg (Lunan) in PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 102 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China Table 1. The description and comparison of the D. subpalmatinervis and P lithophilus. Didymocarpus subpalmatinervis Petrocodon lithophilus Y.M.Shui, The similarity in description W.T.Wang W.H.Chen & Mich.Moller between the two species Habit Perennial, stemless herb Perennial herbs e Leaves shape leaf blade ovate to oblate leaf blade rounded or elliptic * hair adaxially densely appressed pubescent on both surfaces * puberulous, abaxially appressed puberulous, pilose on veins base cordate nearly cordate e margin obtusely or doubly dentate shallowly or deeply crenulate * apex obtuse rounded * Cymes number Cymes ca. 2, ca. 2x branched, 2-10- about10 flowers * flowered; peduncle puberulous pubescent * bracts 2-3, narrowly lanceolate or linear, 2, linear or lanceolate, pubescent * puberulous Calyx Calyx actinomorphic, 5-sect or nearly | Calyx 5-lobed to base, segments e so, segments linear-triangular, both linear, pubescent surfaces puberulous Corolla color Yellow light greenish-yellow e length 2-2: 565M 25-25 6m * 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 adaxial lip 2-lobed, lobes e lobes triangular triangular, abaxial lip 3-lobed, lobes triangular Stamens staminodes Z 3 A Disc annular ring-like e Pistil ovary ovary linear ovary linear inflated e hairs puberulous pubescent * stigma depressed capitate stigma 1, disc-like and undivided * e Completely consistent characteristics; * Overlapping characteristics; A Different characteristics. Chinese, and Y-dje corresponds to Zé Jl] (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 morphologi- cal 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 Didymocar- pus 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. PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 103 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China WM ll l (Elector ¥ ML Sha a WAAiLecaty China Yunnan Shih Govt Malan Stone I wm noe Figure 2. Morphological comparison of Didymocarpus subpalmatinervis and Petrocodon lithophilus A-C, F,-I,: D. sub- palmatinervis D, E, J, F,-I,: 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. PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 104 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China Taxonomic treatment Petrocodon subpalmatinervis (W.T.Wang) F.Wen & Z.L.Li, comb. nov. urn:lsid:ipni.org:names:77326781-1 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.Moller, 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, YM. Shui et al. B2012-078 (KUN: holotype KUN-1519980!; isotype KUN-1519978)). Chinese Vernacular name. 2 /ik GUE: & (Zhang Mai Shi Shan Ju Tai). Distribution and habitat. This species is endemic to Shilin County, Yunnan Province, China, growing in narrow cracks on rocks. Accompanying plants in- clude other shade herbs and trees. Proposed IUCN conservation status. Naigu Stone Forest is a famous sce- nic 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 km? and 30 km*. Despite the severe drought in the second half of 2022 seriously influenc- ing 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)]. Notes. When Wang published the protologue of Didymocarpus subpalmatin- ervis, 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 mis- understanding. 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 ‘2577’; in 1905, he collected Cornus capitata Wall. at the same place (Y-dje near Lou-lan) with the collection number ‘3775’; 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. subpalmatin- ervis with the collection number Fr. Ducloux 3717 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, PhytoKeys 232: 99-107 (2023), DOI: 10.3897/phytokeys.232.108644 105 Zheng-Long Li et al.: Anew combination and a new synonym of Gesneriaceae in China 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. Acknowledgments 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 Profes- sor, 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. Funding This study was financially supported by the Key Science & Technology Research and De- velopment 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 Integra- tive 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. 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