Thalictrum nanhuaense Y.P. Zeng, Q. Yuan & Q.E. Yang, 2021

Zeng, You-Pai, Yuan, Qiong & Yang, Qin-Er, 2021, Thalictrum nanhuaense (Ranunculaceae), a new species from central Yunnan, China, Phytotaxa 479 (1), pp. 121-128 : 121-127

Thalictrum nanhuaense Y.P. Zeng, Q. Yuan & Q.E. Yang , sp. nov., Figs. 1 , 2 .

Type:— CHINA. Yunnan province: Nanhua county, Majie town , Zhongcun village , 24°54′23.77″N, 100°52′12.01″E, in thickets on slopes, 1600 m, 6 August 2020, Y. P . Zeng & Q. L . Huang 460 (holotype IBSC; isotypes IBSC, KUN, PE) .

Description:—Perennial herbs. Roots succulent, tuberose. Stem to 20 cm tall, branched, proximally sparsely pubescent, distally glabrous. Leaves 2‒3-ternate; blade triangular, 3‒8 cm long and broad; leaflets orbicular or broadly ovate, 1‒2 cm long and broad, herbaceous, glabrous on both surfaces, green on adaxial surface, pale green on abaxial surface, base rounded or subcordate, apex obtuse, 3-lobate; lobes entire or inconspicuously 1‒3-crenate; veins flat adaxially, raised abaxially; petiole slender, 3‒7 cm long; stipule membranous, inconspicuous. Inflorescence compound monochasia, corymbiform. Pedicel slender, 1‒2 cm long. Flowers bisexual, erect. Sepals 4‒6, elliptic, ca. 4 mm long, ca. 3 mm broad, white. Stamens 11‒15, ca. 3 mm long; filaments filiform, ca. 2 mm long, white; anthers narrowly oblong, ca. 1 mm long, apex obtuse, pale yellow. Carpels 11‒18, sessile, ca. 2 mm long, glabrous; ovary narrowly fusiform, nearly smooth, ca. 1.5 mm long; style straight, ca. 0.6 mm long; stigma inconspicuous, point-like. Achenes sessile, ca. 3 mm long, glabrous; body subulate-terete, inconspicuously ribbed; style persistent.

Distribution and habitat: Thalictrum nanhuaense is currently known only from its type locality, i.e. Nanhua county in central Yunnan province, China ( Fig. 3 ). It grows in northern subtropical thickets dominated by Dalbergia yunnanensis Franchet (1890: 187) on slopes at an altitude of 1600 m above sea level.

Phenology:—Flowering from July to August; fruiting from August to September.

Etymology:—The specific epithet refers to the type locality of the new species, i.e. Nanhua county in central Yunnan province, China.

Additional specimen examined:— CHINA. Yunnan: Nanhua county, Majie town, Zhongcun village , 24°54′23.77″N, 100°52′12.01″E, X. Gong et al. KIBGX001 B08 ( IBSC) .

Conservation status:— Thalictrum nanhuaense is currently known only from its type locality in Nanhua county in central Yunnan province, China. There are no more than 200 individuals in this population which is situated very closely to farmlands (less than 200 m) and disturbed heavily by grazing and roadbuilding activities. This population is located in the northernmost region of the Ailao Shan , an area not yet well botanized, and we do not know if more populations of this new species can be discovered in the future. The distribution and other information of this species are far from adequate to make a precise and accurate assessment of its risk of threat and endangerment. The conservation status of this species, therefore, should be considered as “Data Deficient ( DD)” and a further investigation on this species is required ( IUCN Standards and Petitions Committee 2019) .

Notes:—From a morphological perspective, Thalictrum nanhuaense is similar to T. fargesii ( Figs. 4 , 5 ) in habit and having larger sepals up to 4 mm long and persistent at anthesis and straight styles, but differs by its succulent and tuberose (vs. fibrous and slender) roots, filiform (vs. clavate) filaments, point-like (vs. oblong and narrowly winged) stigmas, and subulate-terete (vs. lunate-fusiform) achenes. Geographically, T. fargesii is widely distributed in Anhui, Chongqing, Fujian, Gansu, Guizhou, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, and Zhejiang provinces, China ( Wang & Wang 1979, Fu & Zhu 2001, Li et al. 2016, Wang 2018a). Our new species is currently known only from its type locality, i.e. Nanhua county in central Yunnan province, China ( Fig. 3 ). A detailed comparison between the two species is given in Table 1.

Figures

FIGURE 1. Holotype sheet of Thalictrum nanhuaense.

FIGURE 2. Thalictrum nanhuaense in the wild (Nanhua county in central Yunnan province, China, the type locality).A. Habitat. B. Habit. C. Roots. D. Portion of stem. E. Leaf (left: adaxial side; right: abaxial side). F. Leaflet (left: adaxial side; right: abaxial side). G. Flower. H. Sepal (left: adaxial side; right: abaxial side). I. Stamens. J. Carpels. K. Aggregate fruit. L. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 3. Distribution of Thalictrum fargesii (▲) and T. nanhuaense (■).

FIGURE 4. Syntype sheets (A‒D) of Thalictrum fargesii.

FIGURE 5. Thalictrum fargesii in the wild (Pingwu county in northern Sichuan province, China). A. Habitat. B. Habit. C. Roots. D. Portion of stem. E. Leaf (left: adaxial side; right: abaxial side). F. Leaflet (left: adaxial side; right: abaxial side). G. Flower. H. Sepal (left: adaxial side; right: abaxial side). I. Stamens. J. Carpels. K. Aggregate fruit. L. Achenes (immature). Photographed by Y.P. Zeng.