Parnassia farreri is characterised by the petals with long-ciliate petal claw and the broad spatulate staminodes with shallow crenations distally. A sympatric and poorly-known taxon, P. yui, is recorded only from the type collection that morphologically similar to P. farreri. Based on field investigations, examination of herbarium specimens (including the types) and analysis of protologues and distributions, P. yui is hereby reduced to a synonym of P. farreri. Field and anatomy photographs and an updated morphological description of P. farreri are provided. Parnassia farreri is preliminarily designated as Least Concern according to the IUCN Red List guidelines.

Morphology, Parnassia, staminode, synonymy, taxonomic uncertainty

Parnassia L. (Linnaeus 1753) is a fairly homogeneous and distinguishable genus of Celastraceae (APG IV 2016; Ball 2016), consisting of small and glabrous perennial herbs, with a solitary, bisexual and pentamerous flower that has five staminodes borne on an unbranched scape (Ku 1987; Ku and Hultgård 2001). Species of Parnassia predominantly occur in alpine and arctic regions of the Northern Hemisphere, which most diverse in Pan-Himalaya and southwest China (Phillips 1982; Wu et al. 2003; Simmons 2004; Wu 2005). The most recent checklist of Parnassia worldwide was accomplished by Shu et al. (2017) and contains 61 species, two subspecies, 11 varieties and one form. Since then, more than ten names have been reduced to synonyms (Shu et Zhang 2017; Wang et al. 2018; Yu et al. 2018; Ma et al. 2020; Dai et al. 2021) and two new species were described (Zhang et al. 2019).

Parnassia farreri W. E. Evans (1921: 174) was formally described, based on the specimens of R. Farrer 1211 (Fig. 1A) which was collected from Myanmar. The petal base of this species is abruptly contracted into a claw with long ciliated margin, that is distinctive in this genus. Parnassia yui Jien (1963: 256), another species with similar morphological features and neighbouring distribution to P. farreri, was described, based on a single collection (T. T. Yu 20238, Fig. 1B, 24 individuals mounted on four sheets) from Yunnan Province, China. According to the original description, the morphological differences between P. yui and P. farreri include the larger leaves blades (12–24 × 12–24 mm vs. 2–14 × 2–14 mm), the acute or acuminate (vs. rounded) apexes of narrower petals and the three lobed (vs. entire or obscurely sinuate) apex of staminodes.

Figure 1. 

Holotypes of Parnassia farreri (A E00079815) and P. yui (B PE01842927).

Through observation of herbarium specimens, we found these two species are extremely similar in morphology and there is obvious overlap in the shape of leaf blades and staminodes. Therefore, the aim of this study was to clarify the classification relationship between P. farreri and P. yui by re-evaluating their morphological characteristics.

The type specimens of P. farreri and P. yui, along with other related specimens deposited at KUN, PE and SITC, were meticulously inspected. Additionally, digitised material sourced from Herbaria CAS and E (acronyms according to Thiers (2024)) were carefully examined. Field investigations were carried out during September to October of 2024 in Gongshan County, Yunnan Province, China. Eleven individuals with well-preserved leaves and flowers from the type specimens of P. yui and fifty individuals of P. farreri from the wild were used to conduct the morphological measurement and comparison. Eight morphological characters, i.e. leaf length, leaf width, ratio of leaf length/width, petal length, petal width, ratio of petal length/width, number of staminode lobes and depth of staminode lobes were measured in this study. Principal Component Analysis (PCA) was performed to investigate the morphological variations between P. farreri and P. yui.

During the specific field survey of P. farreri populations in southwest China, we documented continuous variations of leaf blades, the shapes of petals and staminodes (Fig. 2A–E), even sometimes within individuals. No specimens of P. yui were traced, except the type materials. Amongst the individuals from the type materials of P. yui, only a few have oblanceolate petals and shallowly 3-lobed staminodes, that match the original description. Additionally, most individuals have triangular-ovate to ovate-spartulate petals, as well as irregular dentate staminodes apexes (Fig. 2F–G). Principal Component Analysis (PCA) could not distinguish these two taxa, the 95% confidence ellipse of P. farreri being almost included in that of P. yui (Fig. 3). Furthermore, the distribution of P. yui is limited in Gongshan County, Yunnan, China and, in this region, more than ten specimens of P. farreri have been collected. The latter taxon is also distributed in Myanmar and India (Shu et al. 2017; Pankaj et al. 2018). Since the lack of clear morphologic distinctions and the overlapping distribution range, we hereby propose to reduce P. yui to a synonym of P. farreri.

Figure 2. 

Morphology of Parnassia farreri A habitat B flower C leaves D variation of petals E variation of staminodes and P. yui F petals G staminodes, photographed from T. T. Yu 20238, the type specimen.

Figure 3. 

The Principal Component Analysis (PCA) plot for the morphological variations between Parnassia farreri and P. yui. The confidence ellipse level is 95%.