Impatiens liupanshuiensis (Balsamianceae), belonging to I. subgen. Impatiens, is recognised as a new species from Guizhou, China and it is described and illustrated. It is morphologically similar to I. xanthocephala W.W. Sm. in its yellow flowers, extremely small basal lobes on lateral united petals, broadly-dolabriform distal lobes and funnelform lower sepal. However, it is distinctive in the number of lateral sepals, teeth on the margin of lateral sepals, the recurvature of the dorsal petal, the number of lateral veins, the shape and size of the lamina and the type of lamina margin. A detailed description of the new species and colour photographs are provided. Its geographical distribution and morphology are also compared to similar species.

China, Flora of Guizhou, Impatiens, morphology, taxonomy

The genus Impatiens Linnaeus (1753: 937–938) (Balsaminaceae) contains over 1000 species distributed primarily in the Old World tropics and subtropics (Grey-Wilson 1980; Yu 2012). A few temperate outliers have also been identified in the Northern Hemisphere (Yu et al. 2016). Five conspicuous diversification centres in the Paleotropical Regions can be recognised: tropical Africa; Madagascar; southern India and Sri Lanka; the eastern Himalaya; and Southeast Asia area in the broad sense (Song et al. 2003; Yuan et al. 2004). In China, 349 species of Impatiens have been recorded (Yuan et al. in press), the overwhelming majority of them being distributed in the southwest region, including Yunnan, Sichuan, Tibet and Guizhou (Chen 2001; Yu 2012). Since 2021, according to our incomplete statistics, eight new species of Impatiens have been described from China (Gu et al. 2021; Liao et al. 2021; Peng et al. 2021a, b; Song et al. 2021a, b, c). In Guizhou, 61 species of Impatiens have been recorded (Peng et al. 2021a; Yu et al. 2021). Additionally, there is one other species of Impatiens from Guizhou currently in press (Ren et al. 2022).

It is well known that Impatiens species are notoriously difficult to classify (Hooker 1908; Grey-Wilson 1980) due to their semi-succulent stems and fleshy leaves, which make it difficult to dry and preserve herbarium specimens. As flowers are extremely fragile, they are difficult to separate and reconstruct from dried specimens, especially when critical floral parts are folded and coalesced. However, since the floral morphology is hyper-variable, the shape and size of petals and sepals are indispensable for identification. Thus, during field exploration, it is essential to make detailed records and separate the parts of the flowers on soft paper in situ.

In September 2016, during a botanical investigation in Zhongshan District, western Guizhou Province, China, we encountered an unusual species, which is only distributed in the Fargesia spathacea Franch. (Poaceae) community in Xiaojiucaiping Mountain, the highest mountain of Guizhou (up to 2900 m alt.). The population of this unusual species is large. It resembles Impatiens xanthocephala W.W. Sm. (1920: 207–208) (Smith 1920) and I. undulata Y.L.Chen & Y.Q.Lu (1990: 23–25) (Chen and Lu 1990) in its yellow flowers, but the highly recurved dorsal petal is distinctive, allowing the anthers to be fully exposed. In September 2020 and August 2021, we revisited Xiaojiucaiping Mountain for a further field investigation to record morphological characters of the species. After careful examination of the relevant specimens and literature (Xiong and Luo 1989; Chen 2001; Chen et al. 2007; Yu 2012; Kuang et al. 2014; Kuang 2015; Luo and Deng 2015; Peng et al. 2021a), the authors decided that the species was hitherto undescribed and close to I. xanthocephala W.W. Sm. Hence, it is described here as a new species with a detailed description and illustrations.

The material for this study was mainly collected in the field at the type locality of the new species in 2020. Herbarium specimens were made carefully. The morphological characteristics of the new species were measured from fresh material and dried herbarium specimens by use of a ruler.

Yu et al. (2016) divided the genus Impatiens into two subgenera, subgen. Clavicarpa S.X. Yu ex S.X. Yu & Wei Wang and subgen. Impatiens, based on the number of carpels, the number of ovules per carpel, the shapes of the capsule, the number of pollen apertures and the pollen grain shape in polar view. In our study, I. liupanshuiensis is nested within subgen. Impatiens by its 5-carpellate ovary, cylindrical capsule and many ovules per locule. The new species is morphologically similar to I. xanthocephala, but I. liupanshuiensis has two lateral sepals with remote teeth on the margin, a more peculiar dorsal petal and more lateral veins and its flowers are shorter than its lamina. I. liupanshuiensis is also similar to I. undulata. To better distinguish the new species morphologically from I. xanthocephala and I. undulata, we list more details in Table 1.

The distributions of these three species are geographically isolated from each other: Impatiens liupanshuiensis is confined to western Guizhou Province, I. xanthocephala is recorded in southwest Sichuan Province and I. undulata is recorded in central Sichuan Province and southern Chongqing Municipality (Yuan et al. in press).

The authors are grateful to Prof. Yuanxin Xiong for assistance on species identification and for providing valuable suggestions. We also thank Wenke Dong, Chenghua Yang and Chaoyi Deng for their helpful suggestions. Additionally, we would like to thank the anonymous reviewers and editors for their constructive comments and suggestions on our manuscript. This research was supported by the National Natural Science Foundation of China (31960328) and Investigation of Wild Ornamental Plant Resources in Guizhou (701256192201).