Cardamine mangshanensis, a new species, is described and illustrated from the limestone landform in southern Hunan, China. The new species is similar to C. macrophylla, but differs from the latter in having more prominent tubers, shorter plant height (10–25 cm vs. 30–95 cm), fewer cauline leaves (3–4 vs. 3–18), crenate leaf margin (vs. serrate), fewer flowers (4–10 vs. 10–30), an earlier flowering period (late February to mid-March vs. April to June) and a shorter growth cycle (ca. 4 months vs. ca. 8 months). Following the IUCN Red List Criteria, C. mangshanensis is assessed as ‘Vulnerable, VU B2ab(ii)’.

Cardamine, limestone landform, new species, taxonomy

The genus Cardamine L. comprises approximately 300 species (https://cardamine.sav.sk), distributed on all continents except Antarctica. According to the Flora of China (Zhou et al. 2001), 48 species have been recorded in China, of which 24 are endemic. Since then, several new species of Cardamine from China have been described, including C. hunanensis (Wu et al. 2021), C. libagouensis (Diao et al. 2023), C. sichuanensis (Guo et al. 2024), C. zhangjiajieensis (Li et al. 2024), and others. Notably, some species within this genus are valued for their edible qualities. For example, in certain regions of southern China, the tender leaves of C. macrophylla Willd. are highly prized by locals for their delicate flavor.

On 25 March 2020, during an investigation in Mangshan National Nature Reserve, we discovered a unique species of the genus Cardamine. This plant had already passed its peak flowering period, with ovaries developing into nascent fruits, indicating that it was different from the plants of the same genus recorded in Hunan Province (Qi and Yu 2002; Wu et al. 2021; Li et al. 2024). To further study this unique discovery, we returned to the same site for an investigation the following year, one month in advance. On 27 February 2021, we successfully collected specimens in flowering season as planned. However, when we returned in mid-April, despite arriving half a month earlier than the previous year, we encountered the same situation: the plants had already entered a state of decay. This prevented us from observing mature fruits and seeds. Nevertheless, based on our comprehensive understanding of its morphological characteristics and phenological patterns, we confidently conclude that this represents a new species.

The specimens are primarily deposited in the Herbarium of Forest Plants at Central South University of Forestry and Technology (CSFI). Morphological observations of the new species were derived from field observations and examination of herbarium specimens. Comparative analyses of related species were examined using online images from JSTOR Global Plants (https://plants.jstor.org/). The conservation status of the new species is based on field observations in accordance with IUCN Red List guidelines (IUCN 2024).

The Flora of China notes that C. macrophylla exhibits a considerable degree of variability, particularly in terms of leaflet number, shape, size, basal structure, and margin characteristics. Special attention is given to the specimen cataloged as Henry 5635, which serves as a key reference in this context. Similar phenomena have been observed in our field studies. However, regardless of the variation in the length of the petioles of the lateral leaflets, the terminal leaflet and the pair of lateral leaflets directly beneath it consistently lack petioles (See Fig. 5A–C). It is also evident that the terminal leaflet is positioned in close proximity to the pair of lateral leaflets below it. Through extensive field research and specimen analysis, we have confirmed that the presence of petioles in the lateral leaflets of C. macrophylla is an individual variation rather than a universal trait. Importantly, the terminal leaflet never has petioles.

Figure 5. 

Leaf morphological variation of Cardamine macrophylla (A–C) and C. mangshanensis sp. nov. (D) A Henry 5635(GH00112001) B Henry 5635(US00100058) C Henry 5635 (K000697746) A–C from JSTOR (https://plants.jstor.org/) D from type locality of C. mangshanensis, photograph by Ang Liu.

However, the terminal leaflet of C. mangshanensis is clearly petiolulate, measuring 0.5–1.5 cm in length. Additionally, the pair of lateral leaflets on its lower side are clearly not closely attached and has petioles that are 0.5–2.5 cm long (See Figs 4A3, 5D). The differences in these traits all prove that C. mangshanensis does not belong to the C. macrophylla complex, but is a new species.

Based on our observations, we have identified a significant correlation between the leaf size of this species and annual precipitation levels. In years with abundant rainfall, such as 2020, the leaves exhibit a marked increase in size, measuring approximately 3–5.5 cm in length and 1.5–2.5 cm in width. In contrast, during years with limited rainfall, such as 2021, the leaves are significantly smaller, ranging from 1.5–2.5 cm in length and 0.5–1 cm in width. This adaptive response to environmental fluctuations highlights the species’ enhanced reproductive capacity and ecological resilience.

These findings provide deeper insights into the complex relationship between morphological traits and environmental factors in C. mangshanensis, and underline its remarkable ability to thrive under varying climatic conditions in limestone landform.

Thanks for PhD Jing Tian’s exquisite preparation of the line drawing and PhD Hong-liang Chen’s great help with this article.