﻿Ranunculusjiguanshanicus (Ranunculaceae), a new species from Sichuan, China

﻿Abstract Ranunculusjiguanshanicus (Ranunculaceae), a new species from Chongzhou in Sichuan province, China, is here described and illustrated. The new species is easily distinguishable from other Chinese members of the genus by an array of characters, including small stature, glabrous and prostrate stems, 3-foliolate leaves with obvious petiolules (3–5 mm long), unequally 3-sected leaflets, lanceolate to linear ultimate leaflet segments, small flowers (5.2–6 mm in diameter), and long styles in the carpels and achenes (ca. 0.8 mm long). A distribution map of this new species is also provided.


Introduction
Ranunculus L., comprising approximately 600 species, is the largest genus in the Ranunculaceae and is widely distributed in all continents (Tamura 1995;Paun et al. 2005;Hörandl and Emadzade 2012). In China, one of the centers of species diversity of Ranunculus, more than 150 species and 30 varieties are currently recognized in the genus (Wang 1995a(Wang , b, 1996(Wang , 2007(Wang , 2008(Wang , 2013(Wang , 2015(Wang , 2016(Wang , 2018(Wang , 2019a(Wang , b, 2022Yang 2000;Wang and Gilbert 2001;Wang and Liao 2009;Luo and Zhao 2013;Wang and Chen 2015;Wang et al. 2016;Yuan and Yang 2017a, b, c;Zhang et al. 2020;Fei et al. 2022Fei et al. , 2023a. During a survey of herbarium specimens of Ranunculus from China for the first author's Ph.D. dissertation project, one gathering, W.B. Ju, L. Zhang & D.K. Chen AZH01290 (CDBI) (Fig. 1), from Jiguan Shan in the Anzihe Nature Reserve in Chongzhou, Sichuan province, China, caught our attention. This gathering had been previously identified on the determination slips as R. glareosus Hand.-Mazz., a species distributed in China's Qinghai, Sichuan, Xizang (Tibet) and Yunnan (Handel-Mazzetti 1931;Liou 1980;Wang and Gilbert 2001). The plants on the two sheets of the gathering, which have unique leaf morphology and very small flowers, certainly do not belong to R. glareosus or any other members of Ranunculus currently known for China.
During a botanical expedition to Sichuan from June to July 2022, we successfully discovered a flowering population of this species in early June on Jiguan Shan in Chongzhou, where the gathering W.B. Ju, L. Zhang & D.K. Chen AZH01290 was made. Moreover, we discovered a fruiting population in early July on Xiling Xue Shan in Dayi, a mountain closely adjacent to Jiguan Shan. Based on our observations of living plants in the wild, we confirmed all the diagnostic characters of the new species observed from the herbarium specimens and determined that the gathering and the two populations in question represent a new species. Morphologically, this new species is somewhat similar to R. pegaeus Hand.-Mazz., a species occurring in southwestern China (Sichuan, Xizang, Yunnan), India (Sikkim) and Nepal (Handel-Mazzetti 1939;Liou 1980;Wang and Gilbert 2001), but differs by an array of characters. It is described below as R. jiguanshanicus.

Materials and methods
For morphological comparison, we critically examined specimens or high-resolution specimen images of Ranunculus glareosus, R. jiguanshanicus and R. pegaeus at CDBI, E, KUN, PE, and WU (acronyms according to Thiers 2022). We also observed living plants in one population each in R. glareosus (Menyuan in Qinghai province) and R. pegaeus (Maoxian in Sichuan province) and those in two populations of R. jiguanshanicus (Chongzhou and Dayi in Sichuan province). The morphological description of R. jiguanshanicus was based on observations of both herbarium specimens and living plants in the wild. Diagnosis. Ranunculus jiguanshanicus is readily distinguishable from all other Chinese species of Ranunculus by a unique array of characters, including small stature, glabrous and prostrate stems, 3-foliolate leaves with obvious petiolules (3-5 mm long), unequally 3-sected leaflets, lanceolate to linear ultimate leaflet segments, small flowers (5.2-6 mm in diameter), and long styles in the carpels and achenes (ca. 0.8 mm long).
Etymology. The specific epithet refers to the type locality of the new species, i.e. Jiguan Shan in the Anzihe Nature Reserve in Chongzhou, Sichuan province, China.
Phenology. Flowering in early June; fruiting at the end of June. Distribution and habitat. Ranunculus jiguanshanicus is currently known from its type locality, i.e., Jiguan Shan in the Anzihe Nature Reserve in Chongzhou, and from the closely adjacent Xiling Xue Shan in Dayi, both in Sichuan province, China (Fig. 6).    It grows among moss on rocks or rocky cliffs in moist places in fir forests at altitudes of 2900-3150 m above sea level.
Conservation status. Ranunculus jiguanshanicus is currently known only from two populations in Sichuan province, China. The Chongzhou population consists of ca. 150 individuals within an area of less than 10 m 2 . The size of the Dayi population remains unknown. The conservation status of R. jiguanshanicus should better be categorized as "Data Deficient (DD)" before adequate information of this species is acquired (IUCN Standards and Petitions Committee 2022).

Discussion.
Ranunculus jiguanshanicus is readily assigned to R. sect. Ranunculus due to its swollen achenes with a distinct beak and receptacles hardly enlarged after anthesis. In his infrageneric classification of the Chinese Ranunculus, Wang (1995a, b) placed almost all the alpine species within this section under the name R. sect. Auricomus (Spach) Schur.