Primula dongchuanensis Z.K.Wu & Yuan Huang, a new species of Primulaceae from Dongchuan of northern Yunnan, China, is described and illustrated. Both morphological and molecular evidence support P. dongchuanensis as a member of the sect. Proliferae. It is similar to P. aurantiaca W.W.Smith & Forrest, but is distinguished by having unique raceme inflorescences. Its distribution, phenology and conservation status are also provided.

Primulaceae, Primula dongchuanensis, new species, Yunnan, China

Primula Linn. is one of the largest genera of Primulaceae, including about 500 species worldwide. Most Primula species are indigenous to the north temperate zone, with only a few outliers on some mountains of Africa (Ethiopia), tropical Asia (Java and Sumatra) and South America (Hu 1994, Hu and Kelso 1996, Mast et al. 2001). The modern center of diversity of Primula is in southwestern China, with ca 300 species of 24 sections, most of which occur in western Sichuan, eastern Xizang, and northwestern Yunnan (Hu 1994, Hu and Kelso 1996). Increased exploration across this region results to the discovery and description of new Primula species in the past 15 years (Hu and Geng 2003, Wu et al. 2013, Xu et al. 2017a, 2017b, Yang et al. 2017, Ju et al. 2018)

Section Proliferae Pax (10:217, 1889) of the genus Primula comprises more than 20 species, mainly distributed in Eastern Himalaya and Hengduan Mountain in China. Most species in this section are horticulturally important plants. Morphologically, sect. Proliferae shows the distinct character of several whorls of flowers in superimposed umbels and is recognized as a ‘natural’ group in this genus. Previous studies presumed that the sect. Proliferae may represent the most primitive group of Primula alive today, and take a central position with respect to subsequent evolution and geographical migration in the genus (Richards 1993, 2002). However, molecular phylogenetic evidence posited the opposite conclusion and indicated that the sect. Proliferae represents relatively advanced members of Primula that exist today (Mast et al. 2001, 2004, Yan et al. 2015).

During the field investigation in the Jiaozi Snow Mountain in Dongchuan of Yunnan, southwestern China in 2011, we found a peculiar population of Primula in its vegetative stage on a small patch of alpine meadow near the mountain top. We transplanted some living individuals to Lijiang Alpine Botanical Garden (at elevation of ca. 3200m), northwest of Yunnan and they regained their bloom in subsequent years. The plant has a short rootstock and robust fibrous roots, obovate-oblong to oblanceolate leaves forming a dense rosette and flowers showed great similarity to the species of sect. Proliferae, except the inflorescences with obsolete scapes at early anthesis, then elongating to forming raceme at late flowering. We presumed the unusual inflorescence springs from abnormal variations of plant response to a different climate zone and soil type after translocation. After the field investigations in the same locality in 2016 and in 2019, we confirmed that the inflorescences we observed from the translocated individuals are morphologically consistent with those of the wild population. Further molecular phylogenic analysis revealed it is an undescribed taxon of sect. Proliferae. We concluded that the species is new to science and describe it here.

Morphological descriptions and comparisons were based on living plants from the Lijiang alpine botanical garden and in the field, specimens from the herbarium of Kunming Institute of Botany, Chinese Academy of Sciences (KUN), and literatures (Chen and Hu 1990, Hu and Kelso 1996). All morphological characters of P. dongchuanensis and its morphological similar species P. aurantiaca were measured using a vernier caliper. The conservation status of P. dongchuanensis was assessed according to the IUCN Red list Categories and Criteria (IUCN 2017).

Genomic DNA was isolated from silica gel-dried leaves using a modified Cetyl Trimethyl Ammonium Bromide (CTAB) protocol (Doyle and Doyle 1987). The nrDNA and two chloroplast matK and trnH-psbA regions of P. dongchuanensis were amplified and sequenced using previously published universal primers (White 1990, Taberlet et al. 1991, Kress and Erickson 2007, Yang et al. 2012). Sequences of the relatives of P. dongchuanensis were downloaded from NCBI (https://www.ncbi.nlm.nih.gov/) (Appendix 1). Sequences for each region were aligned with CLUSTALX (Thompson et al. 1997) and then manually adjusted in BIOEDT 7.0 (Hall 1999). Maximum likelihood (ML) methods for phylogenetic estimation were conducted using IQ-TREE v. 1.6.10 under the GTR+G model (Nguyen et al. 2015). Clade supports were evaluated by 10000 bootstrap replicates of nonparametric approximate likelihood-ratio test (SH-alRT) and ultrafast bootstrap approximation approach (UFBoot) (Guindon et al. 2010; Hoang et al. 2018). Pairwise genetic distances among P. dongchuanensis and its closest relatives revealed by phylogenetic analyses were calculated using the Kimura 2-parameter method (Kimura 1980).

Sect. Proliferae Pax is a taxonomically well-known group in Primula, characterized by numerous whorls of flowers resembling candelabra (Fig. 3) (Chen and Hu 1990). Phylogenetic analyses by using DNA barcoding confirmed the monophyly of sect. Proliferae which could be used in narrowing the scope of identification in Primula (Yan et al. 2015). Preliminary molecular phylogenetic analyses in this study supports the view that P. dongchuanensis is a member of sect. Proliferae, but its molecular closed relatives are not clear yet. Further research is required to clarify the phylogenetic relationship by using enhanced molecular markers with a wider sampling in this section.

Figure 3. 

P. dongchuanensis and four of its close species A P. dongchuanensis B P. aurantiaca C P. cockburniana D P. chungensis E P. pulverulenta.

Morphologically P. dongchuanensis has unique inflorescences architecture compared to other members of sect. Proliferae. The racemose inflorescence appears in some Primula species, but no report in the sect. Proliferae till the addition of P. dongchuanensis, which extended the delimitation of sect. Proliferae and increased our knowledge of the Primula diversity in China. Compared to other species of the sect. Proliferae with bigger and upright inflorescences when anthesis begins, P. dongchuanensis keeps the racemes in a condensed and short form. This could flow from adaptation to the harsh habit of the mountain top where it is usually very windy and insufficient water in late April and May when it starts anthesis, and the other species of sect. Proliferae are usually found in the open and wet alpine meadow and have a late bloom time.

Figure 4. 

Maximum likelihood tree of new Primula species and other Primula species based on nuclear ITS, chloroplast matK and trnH-psbA combined sequenced data, constructed by IQ-TREE under the GTR+G model, clade supports were reported as Shimodaira-Hasegawa approximate Likelihood Ratio Test (SH-alRT)/Ultrafast Bootstrap Approximation (UFBoot), each estimated by 10000 replicates, and only support value more than 50% were reported.

We thank Miss Min Yang for the illustration, Dr. Jie Cai for revision and constructive suggestions to the manuscript. This work was supported by grants from the National Natural Science Foundation of China (31560062), the Yunnan Education Department grant (2015Z057), the Science and Technology planning project of Yunnan Province 2016BC013, and the Major Project on Biodiversity Conservation of Ministry of Ecology and Environment.