Based on a comprehensive morphological and molecular data analysis, we have confirmed and described a new species within the genus Sinocrassula, which is distributed in Sichuan Province, China. Morphologically, the new species resembles Sinocrassula diversifolia and S. indica, but it is distinctly different from them in its asymmetrical leaves, leaf apex with glands, triangular petals that are white at the base and adorned with dense purple-red stripes and spots on the surfaces upward, and rectangular nectar scales. A phylogenetic analysis utilizing four plastid markers and one nuclear marker supports the conclusion that the new species is sister to S. ganluoensis.

Hengduan mountains, phylogeny, rosette, species diversity, taxonomy

Crassulaceae are a morphologically diverse and systematically complex group of angiosperms, comprising 35 genera and approximately 1,400 species (Berger 1930; Eggli 2003; Thiede and Eggli 2007; Messerschmid et al. 2020). Known for their heat resistance and rapid growth, members of the Crassulaceae family are highly adaptable and easy to cultivate. This adaptability makes them excellent for soil improvement and essential components in vertical gardens and green roofs (Zhu 2015). Sinocrassula A. Berger is a small genus within the family Crassulaceae, comprising approximately ten species distributed across various regions, including Bhutan, China, India, Nepal, Pakistan, Sikkim, and Vietnam (Wang et al. 2012, 2022; Fu and Ohba 2013; Averyanov et al. 2014). Despite the distinct characteristics of Sinocrassula, defining monophyletic groups within the genus has proven to be extremely challenging due to the frequent intergradation of morphological traits among taxa, as well as the extensive diversity in morphology and growth habits (Fu and Ohba 2013). Some species of Sinocrassula (e.g., S. indica) have been used as traditional medicine, or enjoyed as a vegetable and infused in herbal teas (Zhao et al. 2004; Xie and Yoshikawa 2012). In recent years, an increasing number of species of Sinocrassula have been discovered in Asia (e.g., S. jiaozishanensis Chao Chen, J. Guan Wang & Z.R. He, S. vietnamensis Aver. & V.V. Byalt) (Averyanov et al. 2014; Wang et al. 2022). The discovery of new species may provide more medicinal resources and increase the species diversity of Sinocrassula.

In July 2023, we conducted two field surveys in Sichuan Province, where we identified two populations of Sinocrassula in Shimian and Hanyuan counties. After carefully culturing the plants and performing a morphological study, we discovered that these populations are distinctly different from all other species within the genus. Additionally, we conducted a phylogenetic analysis, which indicated that these populations form a well-supported clade that is sister to S. ganluoensis (Li et al. 2024). We propose those populations as a new species of Sinocrassula.

A total of 23 accessions representing 12 species from the genus Sinocrassula, along with one outgroup (Kungia aliciae), were included in the phylogenetic analysis. The concatenated dataset was 6,433 bp in length and GTR + F + I + G4 was selected as the best evolutionary model of nucleotide substitutions. The inferred phylogenetic trees from the ML and BI analyses revealed identical topologies. Two samples of the new species formed a highly supported clade (ML-BS = 99; BI-PP = 1.00, Fig. 1), and were found to be sister to Sinocrassula ganluoensis (ML-BS = 100, BI-PP = 1.00, Fig. 1). Then, they together are sister to S. diversifolia (ML-BS = 74, BI-PP = 0.94, Fig. 1). Although the new species is closely related to S. ganluoensis and S. diversifolia, it can be easily distinguished from these two species by its asymmetrical leaves and triangular petals, which are white at the base with dense purple-red stripes and spots on the both surfaces upward. Morphologically, the new species is most similar to S. indica (Table 2). However, the phylogenetic analysis showed that they have a distant relationship (Fig. 1).

Figure 1. 

The maximum likelihood phylogeny of Sinocrassula and its allies based on four chloroplast markers (psbA-trnH, trnL-F, rbcL, and matK) and one nuclear marker (ITS). Values associated with branches are Maximum Likelihood Bootstrap Support (ML-BS) and Bayesian Inference Posterior Probability (BI-PP). Bold indicated it received full ML-BS and BI-PP support.

The new species exhibits some typical characteristics of Sinocrassula including compact rosette, stem leaves alternate and lanceolate, bracts resembling distal stem leaves but smaller, flowers 5-merous, broadly triangular sepals, and ovoid carpels (Fu and Ohba 2013). A comparison of morphological characters among the new species and its morphologically similar species is shown in Table 2. The new species can easily distinguished from other species by its unique combination of asymmetrical leaves, rectangler nectar scales, and triangular petals which are white at the base and gradually transition to purple toward the tips (Fig. 2).

Figure 2. 

Sinocrassula obliquifolia A, B habit C, D flowers E stamen F, G petals H carpel I sepal J nectar scale K basal leaves L stem leaves M gland of basal leaf N leaves that abscise and bud during the flowering period, left: basal leaf, right: stem leaf.

We thank Yi Liu for help in the field. Three anonymous reviewers and an editor are thanked for their helpful suggestions.