﻿Epimediumlongnanense (Berberidaceae), a new species from Gansu, China

﻿Abstract Epimediumlongnanense, a new species of Epimedium (Berberidaceae) from Longnan Prefecture, Gansu Province, China, is here proposed and illustrated. E.longnanense has large flowers with petals possessing long spur and obvious basal lamina, and thus should be grouped into series Davidianae. The species closely resembles E.flavum of ser. Davidianae in morphology. However, it can be easily distinguished by its elongated rhizome (vs. compact), trifoliolate leaves (vs. five leaflets, sometimes trifoliolate), pale pink or purplish-red inner sepals with 6–8 × 2–3 mm (vs. pale sulphur-yellow, ca. 11 × 4 mm).

and intermittently distributed in a narrow strip between Japan in Asia and Algeria in northern Africa (Ying 2002). With about 52 species, China is the center of diversity and distribution for Epimedium (Ying et al. 2011;Zhang et al. 2022b). Epimedium plants are excellent horticultural crops due to their beautiful and diverse leaves and flowers . Epimedium has also been reported to have important medicinal values, such as strengthening the kidneys, curing rheumatism, and helping to fight osteoporosis, and tumors (Zhang and Yang 2021;Zhao et al. 2022).
In June 2021, we collected an unusual plant of Epimedium from Kangnan Forest District, Longnan Prefecture, Gansu province, China. In June 2022, we went to the forest district on two further occasions to investigate this plant of Epimedium. The plant is a low-growing herb with a height of 15-20 cm, bearing slender and elongated rhizomes. Its leaves are trifoliolate, and the leaflets are broadly ovate or almost orbicular and relatively small (2.4-4 × 2.3-4 cm). Furthermore, the plant possesses large yellow flowers and its petals are long spurred with an obvious basal lamina, and thus should be a member of ser. Davidianae Stearn. However, this plant has obvious morphological differences from other species of ser. Davidianae by its elongated rhizome, leaflet number, leaflet morphology, leaf arrangement on the flowering stem, flower color, and shape and size of inner sepals and petals. We confirmed that the plant should be a new species, which we describe below.

Materials and methods
We have been engaged in taxonomic research of Chinese Epimedium since 2004. We examined all the specimens of Epimedium from the main herbaria of China (BCMM,  CDCM, CDBI, GXMI, GZTM, HGAS, HGCM, HIB, HNNU, HNWP, HWA,  IBK, IMD, KUN, PE, SAU, SM and SZ). Other Epimedium herbaria of China were examined from the Chinese virtual herbarium (http://www.cvh.ac.cn/). We also investigated the images of specimens of Epimedium from K, P, WU and WUK obtained by email or their network databases. In total, about 1700 Epimedium specimens have been intensively studied. Furthermore, our field investigations covered most of the distribution regions of Chinese Epimedium, including the following provinces, Anhui, Chongqing, Gansu, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangxi, Jilin, Liaoning, Shanxi, Shaanxi, Sichuan and Zhejiang of China. Almost all of the Chinese species of Epimedium were collected and transplanted to Wuhan Botanical Garden, the Chinese Academy of Sciences, for further study and conservation. For the new species of Epimedium, we compared its morphological characters with other species of the genus based on the specimen review and cultivation observation, as well as investigating its distribution and habitat. The morphological characters were described using the terminology used by Stearn (2002), Ying et al. (2011) and Zhang et al. (2022b). Diagnosis. Epimedium longnanense is closely similar to E. flavum Stearn in morphology, but can be easily distinguished by its elongated rhizome, trifoliolate leaves, and relatively smaller and pale pink or purplish-red inner sepals.
Phenology. Flowering in June; fruiting in late June and early July. Etymology. Longnan is located in the southeast of Gansu Province, the intersection of Qinba Mountain, Loess Plateau and Qinghai Tibet Plateau in China. Longnan is a biodiversity hotspot where many new species or new species records have been found (Liu et al. 2018;Qin et al. 2020;Zhang et al. 2022a). The new species, E. longnanense, is found in this region and is named after the geographic name.
Distribution and habit. At present, Epimedium longnanense is only known from its type locality, i.e. Kangnan Forest District, Kangxian County, Longnan Prefecture, Gansu Province, China. The new species mainly occurs in thickets at elevations of 1800-2300 m and is usually together with Fargesia nitida (Mitford) Keng f. ex Yi, Rubia cordifolia L., Smilax stans Maxim., Cardamine tangutorum O. E. Schulz and Veratrum nigrum L. It often grows in stone crevices with barren soil, and its elongated and slender rhizome might be an adaptive characteristic of its living environment. Except for E. longnanense, there are two other species of Epimedium, E. brevicornu Maxim. and E. pubescens Maxim., in Gansu Province, China. In the type locality of E. longnanense, we also found E. pubescens at elevations of 300-1500 m, but no sympatric distribution of these two species was found.

Discussion
The floral trait is one of the most stable taxonomic characters in Epimedium, which has abundant diversities and is the focus of evolution studies of the genus (Ying 2002;Zhang et al. 2014;Guo et al. 2022). In the updated taxonomic system of Epimedium (Stearn 2002), all species endemic to China were classified into section Diphyllon Stearn of subgenus Epimedium Stearn. The section was divided into four series according to the flower morphology: ser. Campanulatae Stearn is characterized by campanulate flowers and flat petals without spur; ser. Davidianae Stearn bears large flowers and long spurred petals with obvious basal lamina; ser. Dolichocerae Stearn possesses large flowers and long spurred petals with no basal lamina; and ser. Brachycerae Stearn is characterized by short and spurred or saccate petals that are much shorter than the inner sepals. Epimedium longnanense has large flowers with petals possessing long spur and obvious basal lamina, and thus should be grouped into ser. Davidianae. So far, in total, there are 16 species in ser. Davidianae (Stearn 2002;Guo et al. 2007;Zhang and Li 2009;Ying et al. 2011;Zhang et al. 2016Zhang et al. , 2022b. Among these 16 species of Epimedium ser. Davidianae, E. longnanense is the most closely similar to E. flavum Stearn in morphology. However, E. longnanense can be easily distinguished by its rhizome, leaf and flower characters (Table 1). E. longnanense has a slender and elongated rhizome ca. 1 mm in diameter, while E. flavum has a compact rhizome 2-4 mm in diameter. Although their leaflets are similar in shape and size, E. longnanense has trifoliolate leaves, and E. flavum bears leaves usually with five leaflets, sometimes three leaflets. Furthermore, E. longnanense has smaller and pale pink or purplish-red inner sepals (6-8 × 2-3 mm), and its petals have spurs much longer than inner sepals (1.5-2.5 cm), while E. flavum has pale sulphur-yellow and larger sepals (ca. 11 × 4 mm), and its spurred petals are slightly longer than its inner sepals (ca. 1.3 cm).
Among the other three series of Chinese Epimedium sect. Diphyllon, E. longnanense closely resembles E. membranaceum in morphology, a species in ser. Dolichocerae. Epimedium membranaceum was treated as a synonym of E. davidii Franchet in Flora Reipublicae Popularis Sinica (Ying 2001) and Flora of China (Ying et al. 2011). However, E. membranaceum and E. davidii are two distinct species with obvious differences in leaflet number and floral characters (Stearn 2002;Zhang et al. 2015). Both E. longnanense and E. membranaceum have large yellow flowers, and their petals possess long, slender and slightly-curved spurs. However, E. longnanense is only 15-20 cm high with shorter inflorescence (10-15 cm), while E. membranaceum is taller (20-65 cm) with longer inflorescence (16-30 cm). Furthermore, E. longnanense has petals possessing an obvious basal lamina and is a member of ser. Davidianae, while E. membranaceum has petals with no lamina and is a member of ser. Dolichocerae (Table 1).