Primula is a genus of roughly 549 species distributed primarily across temperate and alpine regions of the Northern Hemisphere, with China alone harboring about 351 species classified into 24 sections. Approximately 75 percent of the Chinese species are endemic to the country, and southwestern China, especially the Himalayan-Hengduan Mountains region, serves as both a center of differentiation and a modern distribution center for the genus. Guizhou Province, famous worldwide for its karst topography, hosts about 30 documented Primula species, all of which occur in karst habitats. The heterogeneous microhabitats created by millions of years of limestone dissolution have facilitated rapid diversification and speciation, producing endemic species such as P. esquirolii, P. fangingensis, P. kweichouensis, P. lithophila, and P. levicalyx, along with recent additions including P. chishuiensis, P. pingbaensis, and P. xinjingensis.

The story of the new species began in December 2017, when one of the authors of the study encountered a distinctive dwarf primrose growing in moist crevices on shaded karst cliffs near Xingyi. The plant was immediately unusual: gracile and low-growing, with small suborbicular leaves that were purplish on the underside, densely covered with long villous hairs on both surfaces, and heart-shaped at the base. The flower stalk, or scape, was remarkably short, and the flowers were long-styled and homostylous, meaning that every individual flower carries a single floral form with a style that protrudes well beyond the corolla tube. Between 2023 and 2026, the research team conducted repeated field investigations at the type locality and surrounding areas during December and from March to April, over four consecutive years, to confirm the floral and fruit characteristics of the species.

Those follow-up surveys delivered the decisive diagnostic evidence. The team confirmed that the capsule of the plant dehisces calyptrately, meaning it opens by a lid rather than by valves or by crumbling. This calyptrate capsule is the defining character of Primula sect. Carolinella, a small group of approximately 14 species worldwide. After consulting the relevant literature and examining herbarium specimens, the authors concluded that the plant belongs to sect. Carolinella and represents a taxon new to science, which they described and illustrated as Primula xingyiensis Z.K.Wu & C.Y.Deng. The specific epithet derives from Xingyi, the county in southwestern Guizhou where the type specimen was collected, and the species carries the Chinese vernacular name xing yi bao chun.

The morphological description, based on measurements of 15 randomly selected living individuals, portrays a perennial herb that is completely efarinose, meaning it lacks the powdery white farina characteristic of many Primula species, and instead bears pubescent and glandular hairs on its aerial parts. The rhizome is short and fleshy, 1 to 1.5 centimeters long, bearing a basal rosette of leaves with petioles 1.5 to 3.5 centimeters long that are densely villous and purplish-red. The leaf blades measure only 1.1 to 1.7 centimeters in both length and width, with rounded apices, cordate bases, entire margins, and two to three pairs of lateral veins that are prominent and purplish-red on the underside. The narrowly campanulate calyx is just 2 to 3 millimeters long, divided to one-third or one-half of its length into narrowly triangular lobes.

The corolla is the feature that most dramatically separates the new species from its relatives. Pink with a white tube, the salverform corolla has a tube 1.5 to 2.3 centimeters long, which is 7 to 8 times as long as the calyx, an extraordinary proportion within the section. The limb spans 1.1 to 1.6 centimeters in diameter, with oblong lobes that are deeply emarginate at the apex. The anthers sit at the throat of the corolla tube, and the style, 2 to 2.5 centimeters long, is slightly exserted from the tube. The capsule is small, about 2 millimeters in diameter, and dehisces circumscissilely, while the seeds measure roughly 0.3 millimeters in diameter with a smooth surface. Flowering occurs from December to January, and fruiting from February to April, making this a winter-blooming primrose.

Primula xingyiensis is most similar morphologically to P. intanoensis from Thailand and P. calyptrata from Yunnan, which are the other long-styled homostylous species within sect. Carolinella, sharing cordate leaves with long petioles, pubescent indumentum, and campanulate or narrowly campanulate calyces. The new species differs from both by its dwarf and gracile habit, its small leaves up to only 1.7 centimeters wide, its shortened scape measuring just 1 to 2 centimeters, its shorter calyx of 2 to 3 millimeters, and its long corolla tube. The contrasts are stark: P. intanoensis has a scape about 5 centimeters tall with a white corolla whose tube is only 1 to 1.5 times the calyx length, while P. calyptrata has a scape of 12 to 18 centimeters with a purple corolla whose tube is roughly 3 times the calyx length. P. xingyiensis, by comparison, has a scape up to 3 centimeters tall with purplish-red leaf undersides and pink flowers. To aid identification, the authors constructed a key to all 15 known species of the section.

The taxonomic placement of the new species carries broader significance for primrose systematics. Molecular phylogenetic studies have shown that calyptrate capsule dehiscence is polyphyletic, meaning the lid-opening capsule evolved independently more than once, and that the species of sect. Carolinella do not form a monophyletic group. Instead, they are dispersed across four clades embedded within subgenus Auganthus, suggesting that the section should ultimately be merged into that subgenus. Morphologically, apart from the calyptrate capsule, characters of sect. Carolinella such as long petioles, pubescent leaves, cordate leaf bases, and the absence of farina are indeed more consistent with subgenus Auganthus, a resemblance that historically led some members, including P. kwangtungensis and P. kweichouensis, to be placed in sect. Obconicolisteri for decades. Pollen morphology within the section is polymorphic, with polycolpate pollen of multiple origins, further indicating the heterogeneity of the group. Because no formal molecular-based infrageneric treatment of Primula has yet been published, however, the delimitation of sect. Carolinella still relies on traditional taxonomic concepts, which is why the authors placed P. xingyiensis in this section pending future phylogenetic studies with comprehensive sampling.

Field surveys in Xingyi and nearby karst areas of southwestern Guizhou have so far located the new species at only two populations near the type locality, where it grows in moist crevices on shaded cliffs at elevations between 1200 and 1300 meters. The total number of mature individuals across the two populations is fewer than 200. Applying the IUCN Red List Categories and Criteria, the authors assessed the species as Critically Endangered under criterion B2ab(i, ii, iii), based on an area of occupancy smaller than 500 square kilometers, severely fragmented habitat, and continuing decline in the extent of occurrence, the area of occupancy, and the quality of habitat. The main threats identified are microhabitat drought resulting from climate change and human disturbance.

The discovery underscores both the botanical richness of Guizhou’s karst landscapes and their fragility. Nearly a decade of field observations indicate that P. xingyiensis is restricted to a highly specialized microhabitat, shady and moist crevices of karst cliffs, where the same geological features that fostered its evolution now confine it to a handful of sites vulnerable to drying conditions and human activity. As one of only a few winter-flowering homostylous primroses known from China, and the fifteenth species in a section whose evolutionary history is still being untangled, P. xingyiensis joins a growing roster of karst endemites whose survival depends on the protection of these limestone microhabitats. The authors note that a more robust delimitation and subdivision of sect. Carolinella will depend on future phylogenetic studies, and that continued exploration of Guizhou’s heterogeneous karst habitats may yet reveal further species new to science.

Subject of Research: Botany

Article Title: Primula xingyiensis ( Primulaceae ), a new species in Primula sect. Carolinella from Guizhou, China

Article References: Shi, X.-T., Deng, C.-Y., Lang, Y.-X., Liu, Z.-C., & Wu, Z.-K. (2026). Primula xingyiensis (Primulaceae), a new species in Primula sect. Carolinella from Guizhou, China. PhytoKeys, 276, 1-11. https://doi.org/10.3897/phytokeys.276.195710

Image Credits: AI Generated

DOI: 10.3897/phytokeys.276.195710

Keywords: Primula, new species, Guizhou, China, karst, Primulaceae, biodiversity, taxonomy, conservation, PhytoKeys, xingyiensis, species