Polygala spatulata Y. Nong & Run Hua Jiang (sect. Pseudosemeiocardium, Polygalaceae), a new species from a karst cave in west Guangxi, China, is described and illustrated. This new species resembles Polygala isocarpa Chodat in its annual habit, terminal racemes, lamellate appendage, yellow flowers and glabrous seeds, but it can be easily distinguished by its sparsely white-pilose stem and leaf blades, spoon-shaped inner sepals, ovate outer sepals (ca. 1.5 mm) which is glandular and all persistent after anthesis, as well as its elliptic, reticulate seeds. Photographs, an illustration, a distribution map and a comparative table with the most similar species are also provided.

Karst cave, new species, Polygala, taxonomy

Polygala L. is one of the most diverse genera in the family Polygalaceae, with an almost global distribution (Anderson and Cronquist 1982). While the exact number of species remains contested due to ongoing discussion of genus delimitation, recent evaluations recognise between 422 and 552 species (Pastore et al. 2019; POWO 2024). Molecular phylogenetic studies consistently demonstrate Polygala’s polyphyletic nature, identifying three well-supported clades: a New World clade (NWC), an Old World clade (OWC) and a third clade comprising Polygala subg. Chodatia (Eriksen 1993; Persson 2001; Forest et al. 2007; Pastore et al. 2019; Martinez et al. 2022). The OWC, the most species-rich clade, is distributed across Europe, Africa and Asia (Lyskov et al. 2019). Pastore et al. (2019) consider all NWC species as also part of Polygala subg. Polygala. The Polygala NWC includes 213 species that may be divided into three sections: Clinclinia DC., Monninopis A.Gray, and Timutua DC. The Polygala OWC includes the type of the genus Polygala vulgaris L. and its ca.349 species are divided into 11 sections: Blepharidium DC., Brachytropis DC., Chloropterae (Chodat) Paiva, Conosperma Paiva, Leptaleae (Chodat) Paiva, Madecassa H.Perrier, Megatropis Paiva, Microlophium Spach, Polygala, Psychanthus (Raf.) DC. and Tetrasepalae (Chodat) Paiva.

Adema (1966) recognised 10 sections in Polygala and described a new section Pseudosemeiocardium Adema, later elevated to the status of subgenus by Chertk and Křísa (1977) and eventually segregated into the genus Heterosamara Kuntze emend. Heterosamara has been effectively used since Paiva (1998) and is recognisable by the heteropolar pollen with bilateral symmetry. Pastore et al. (2019) suggests for the first time that Heterosamara may not be monophyletic, forming a paraphyletic grade with Polygala sect. Chodatia and Polygaloides and before proposing formal taxonomic changes, their findings need to be further tested.

According to the Flora of China, species of Sect. Pseudosemeiocardium Adema are recognisable by annual herbs, often branching in corymbose fashion from the middle. Flowers are small, yellow, rarely purple-red, with one outer sepal persisting after flowering; seeds often have papillary or helmet-shaped caruncles. About seven species are distributed across the southern slopes of the Himalayas, northern India, the Indochina Peninsula, Malaysia, the Philippines, Indonesia, western Papua New Guinea and Japan. Five species are native to China, distributed throughout the country, but most abundant in the southwest (Chen et al. 1997).

Forty-two species and eight varieties of Polygala were found in China, widely spread across the country, but most abundant in the south-western and southern regions (Chen et al. 1997), 44 species of Polygala were recognised, with 21 endemic to China in the flora of China (Chen et al. 2008), but most recently, one new species was identified from China (Liu et al. 2024). During our field surveys in Bama County, Guangxi in August 2024, we discovered a special Polygala population in a karst cave, this population of plants resembling Polygala isocarpa Chodat in being an annual herb with terminal racemes, lamellate appendage, yellow flowers and glabrous seeds. However, it differs distinctively by its sparsely white-pilose stem and leaf blade, with outer sepals remaining persistent after anthesis. After consulting relevant literature (Chen et al. 1997; Chen et al. 2008; Liu et al. 2024) and checking relevant specimens, we confirm that this unusual plant represents a new Polygala species, which we describe and illustrate below.

The new species was described, based on field observations that were made in August 2024 and examination of herbarium specimens at GXMI. Other related Polygala species were examined, based on online images from the Kew Herbarium Catalogue (http://apps.kew.org/herbcat/gotoHomePage.do) and JSTOR Global Plants (http://plants.jstor.org/). Morphological characters that distinguish it from all other species in the genus of Polygala are used. We also observed living plants of the new species at flowering and fruiting time (August and September). We observed characters of stem, petiole, leaf, racemes, pedicel, bracts, sepals, petals, stamens, ovary, style, capsule and seeds.

Descriptions were written, based on herbarium specimens. Measurements were made with a tape measure and callipers. The structure of the indumentum and its distribution were observed and described under a dissecting microscope at magnifications of more than 20×. Additional information on locality, habitat, ecology, plant form and fruits were collected in the field and taken from herbarium labels. The conservation threat assessment followed IUCN Categories and Criteria (IUCN 2022).

We are grateful to Xiang-chun Lan for fieldwork assistance and Xin-cheng Qu for the line drawing (Guangxi Institute of Traditional Medical and Pharmaceutical Sciences, Nanning).