Petrocosmeaduyunensis (Gesneriaceae), a new species from Guizhou, China

Abstract Plants belonging to the genus Petrocosmea are rare and small herbs difficult to find in the wild. In the present study, a new species, Petrocosmeaduyunensis, from Guizhou, China, is described. The species is most similar to P.leiandra and differs from it by a distinctly recurved abaxial corolla lip, free anthers and included pistil. Detailed morphological comparisons are given. One population with about 100 mature individuals was found at the type locality. This new taxon was assessed as “Data Deficient” (DD) according to the IUCN standards.


Introduction
The genus Petrocosmea Oliv. belongs to the family Gesneriaceae, subfamily Didymocarpoideae (Weber et al. 2013). According to an earlier revision of the genus by Wang (1985), 27 species and four varieties were recognised and classified into three sections, viz., sect. Anisochilus Hemsl., sect. Deinanthera W.T.Wang, and sect. Petrocosmea. In 2015, the first phylogenetic analyses of the genus were presented, 33 species and three varieties were classified into five sections, viz., sect. Petrocosmea Oliv., sect. Anisochilus Hemsl., sect. Minor Zhi J. Qiu, sect. Barbata Zhi J. Qiu, and sect. Deinanthera W.T. Wang (Qiu and Liu 2015;. Presently, the genus comprises 56 species with three varieties (GRC 2021). Its native range is from the eastern Himalayas to central China and Indo-China (POWO 2021). The distribution of most of Petrocosmea species is restricted to relatively small geographical areas (Wang et al. 1998;Wei and Wen 2009). South and southwestern China are the centres of gesneriad diversity (Xu et al. 2017). Guizhou is a province that lies in the southwest of China. To date, 14 taxa of Petrocosmea have been recorded in Guizhou, and the type localities of eight taxa were in Guizhou (Wang 1984;Gou et al. 2010;Han et al. 2017Han et al. , 2019. In November 2020, during field work in Duyun county, Guizhou province, we collected some living plants belonging to the genus Petrocosmea. In April 2021, when the plants flowered in the greenhouse of the Guizhou Botanical Garden, they had distinctly recurved abaxial corolla lips and included pistil. In the same month, we visited the type locality again and collected flowering specimens. The plants were classified as belonging to sect. Minor, which mostly possesses a highly fused upper lip and forms a carinate-plicate shape on the upper lip. They were most similar to P. leiandra (W.T.Wang) Z. J. Qiu in the shape of leaf blades and corolla limb, and anther dehiscence. After thorough comparisons, we concluded that the plants represented a new species.

Methods
Morphological observations of flowering plants were performed in the field and in the greenhouse. All morphological characteristics were observed under a dissecting microscope (Olympus SZ61, Tokyo, Japan), and descriptions were made following the terminology used in Wang et al. (1998) Huang and Xin (2021), in addition to those mentioned in the introduction. The images of type specimens available in virtual herbaria and databases, including RBGE (https://data.rbge.org.uk/search/ herbarium/), Kew Herbarium Catalogue (http://apps.kew.org/herbcat/navigator.do), MNHN (https://www.mnhn.fr/en), PE (https://pe.ibcas.ac.cn/index.html), and iPlant (http://www.iplant.cn/) were also examined. In order to obtain comparable morphological data for living plants, flowering plants belonging to the new taxon and similar species were collected from their type localities. The type specimens of the new taxon were collected by Sheng-Hu Tang in the field.
Phenology. Flowering from April to May, fruiting in the wild is unknown, only capsules of the previous year were observed.
Etymology. The new taxon is named after the type locality, Duyun county, China. Conservation status and IUCN Red List category. One population with about 100 mature individuals was found at the type locality. The habitat is in a nature reserve protected by the local government. It is highly likely that more populations are present in the area. Before further investigations, this species should be assessed as "Data Deficient" (DD) according to the IUCN standards (IUCN 2019).
Notes. Although Petrocosmea duyunensis has a short adaxial corolla lip, the pistil is still included in the corolla. This is because the style is relatively short and distinctly curved. The plant possesses two free anthers. These characteristics differ from those of other Petrocosmea species. Morphologically, the species is similar to P. leiandra (Fig. 2), and detailed morphological comparisons are shown in Table 1.

Acknowledgments
This work was supported by Guizhou Provincial Science and Technology Projects, Guizhou Academy of Science ([2019]07) and Guizhou Science and Technology Department ([2017]2523 and QKHJC[2020]1Y066). We are grateful to Michael Möller and Lei Cai for careful corrections and suggestions. We would like to thank Fang Wen for checking specimens, and Bin-Jie Ge for delivering specimens of the new taxon.