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

Zeng, You-Pai, Yuan, Qiong & Yang, Qin-Er, 2021, Thalictrum bouffordii (Ranunculaceae), a new species from the Qionglai mountains region in western Sichuan, China, Phytotaxa 510 (1), pp. 18-28 : 18-26

Thalictrum bouffordii Y. P. Zeng, Q. Yuan & Q. E. Yang , sp. nov. ( Figs. 1‒4 ).

Type:— CHINA. Sichuan: Tianquan county, Xingou town , along G318 highway, near Chizhuping , 29°53′16.75″N, 102°21′21.77″E, on moist cliffs in ravine, 1690 m, 6 July 2020, Y. P. Zeng & Q. L. Huang 352 (holotype IBSC, barcode unavailable; isotypes CDBI, IBSC, PE, barcodes unavailable) .

Description:—Perennial herbs. Roots fibrous. Stem to 100 cm tall, striate, distally branched. Leaves 2‒4-ternate; blade triangular, 10‒25 cm long and broad; leaflets ovate, broadly ovate or rhombic, 1‒3 cm long, 0.8‒2.5 cm broad, papery, both sides glabrous, green on adaxial side, pale green on abaxial side, base rounded or subcordate, apex obtuse or acute, 3-lobate; lobes entire or 2‒3-lobate, apex obtuse or acute; veins flat adaxially, slightly raised abaxially; petiole slender, 1.5‒10 cm long; stipule membranous, margin torn. Inflorescence a many-flowered corymbiform compound monochasium, dichotomous; rachis glabrous or sparsely pubescent. Pedicels 0.8‒1.5 cm long, glabrous or sparsely pubescent. Flowers bisexual, erect. Sepals 4‒5, caducous, cymbiform-elliptic, ca. 4 mm long, ca. 2 mm broad, whitish tinged with purplish to distinctly purple, abaxially pubescent. Stamens ca. 60, 6‒ 7 mm long; filaments clavate, ca. 5.5 mm long, purplish; anthers oblong, ca. 1.5 mm long, apex obtuse, white. Carpels 6‒10, sessile, ca. 2 mm long; ovary lunate-fusiform, shallowly ribbed, ca. 1 mm long, glabrous or sparsely pubescent; style ca. 1 mm long, recurved at apex; stigma conspicuous, linear, ca. 0.5 mm long. Immature achenes sessile, ca. 3 mm long; body fusiform, profoundly ribbed, pubescent; style persistent, recurved at apex.

Distribution and habitat:— Thalictrum bouffordii is currently known from Luding, Shimian and Tianquan counties in the Qionglai mountains region in western Sichuan, China ( Fig. 5 ). It grows along forest margins or on moist cliffs in ravines at altitudes of 1360‒3200 m above sea level.

Phenology:—Flowering from June to October; fruiting from July to November.

Etymology:—It is a great privilege to name our new species in honor of Dr. David E. Boufford with Harvard University Herbaria, one of the greatest hunters of Chinese plants. His specimens of Chinese plants are among the finest ever made, a real joy to study. As a member of the editorial board of the Flora of China completed in 2011, Dr. Boufford is also a very active researcher of Chinese plants and a most helpful friend of many Chinese plant taxonomists, including the third author of this paper.

Additional specimens examined:— CHINA. Sichuan: Luding, K.Y. Lang, L.Q. Li & Y. Fei 1351 (KUN0689899, PE01108835, PE01108836), G.H. Xu 26353 (CDBI0026148, CDBI0026149); Shimian, C.C. Hsieh 41833 (IBSC0090544, PE00471029, PE00471091, SZ00092282, SZ00092301, WUK, barcode unavailable), Shimian Exped. 78-1050 (SM704604597, SM704604743); Tianquan, D.F. Chamberlain & F.T. Pu 148 (CDBI0026494), X.J. He & Q.S. Zhao 171869 (SZ00571393, SZ00571413, SZ00571414, SZ00571415), X.J. He & Q.S. Zhao 190519 (SZ00578647, SZ00578648), X.J. He & Q.S. Zhao 192292 (SZ00571336, SZ00571337, SZ00571338), K.C. Kuan & W.T. Wang 3247 (K, barcode unavailable, PE00471028, PE00471030), N. Liu ELS008 (BNU0020049), C. Pei 8268 (NAS00187295, NAS00187297, SZ00092590), D.Y. Peng 46583 (CDBI0026159, IBSC0090429), Sichuan Econ. Plant Exped. 540 (PE00471031, PE00471033), P.C. Tai & C.M. Teng 4378 (SZ00092589), H.L. Tsiang 34799 (IBK00012648, IBSC0090351, PE00471035, SZ00092274), H.L. Tsiang 35238 (NAS00187277, PE00470992, SZ00092272), Y.P. Zeng & Q.L. Huang 355 (IBSC, barcode unavailable).

Conservation status:— Thalictrum bouffordii is currently known from Luding, Shimian, and Tianquan counties in the Qionglai mountains region in western Sichuan, China. The two populations in Luding and Tianquan, which we visited in 2020, consist of at least 100 individuals each. However, the size of the population in Shimian remains unknown. The conservation status of T. bouffordii should be considered as “Data Deficient (DD)” before adequate information of this species is acquired ( IUCN Standards and Petitions Committee 2019).

Notes:— Thalictrum bouffordii is most closely similar to T. xinningense Wang (2017: 408) ( Figs. 6‒8 ) in habit and having clavate filaments, apically recurved styles, and sessile, profoundly ribbed and pubescent achenes, but differs by having proximally glabrous (vs. densely pubescent) stem ( Figs. 3D , 7D ), inflorescence a many-flowered corymbiform compound monochasium (vs. a thyrse) ( Figs. 1 , 2 , 3B , 4B , 6 , 7B , 8 ), abaxially pubescent (vs. glabrous) sepals ( Figs. 3I , 4G , 7I ), and purplish (vs. white) filaments ( Figs. 3J , 4H , 7J ) (also see Wang 2017, 2018a). Geographically T. bouffordii occurs in western Sichuan, whereas T. xinningense is widely distributed in southern Chongqing, northern Fujian, northern Guangdong, northern Guangxi, eastern Guizhou, southwestern Hubei, Hunan, northern Jiangxi, and southern Zhejiang ( Zeng et al. 2020a); both species are thus geographically isolated from each other ( Fig. 5 ).

As mentioned above, specimens of Thalictrum bouffordii had all been previously misidentified as T. javanicum . Indeed, T. bouffordii is somewhat similar to T. javanicum in habit, but differs by having abaxially pubescent (vs. glabrous) sepals, purplish (vs. white) filaments, and pubescent (vs. glabrous) achenes (also see Backer & Bakhuizen van den Brink 1963). Moreover, as noted by Zeng et al. (2020b), previous records of the occurrence of T. javanicum in China might be a mistake caused by the misapplication of this name to the relevant Chinese populations. The descriptions of T. javanicum in the Chinese floristic works by various authors, including Anonymous (1972, 1976, 2014), Wang & Wang (1979), Wang (1985, 1991, 1993, 2000, 2003, 2004, 2018a), Lin & Zhao (1985), Li (1986), Lin (1992), Liu (2000), Fu & Zhu (2001), Luo & Luo (2008), Wang & Liu (2016), and Xie et al. (2016), have been made mainly based on Chinese specimens, not on material from the type locality, i.e. Java in Indonesia. These Chinese specimens actually belong to T. nepalense Wang (2018b: 641), T. xinningense , and our new species as well, respectively. An identification key to T. bouffordii and its closely similar species including T. javanicum , T. nepalense and T. xinningense is given below.

Figures

FIGURE 1. Selected specimens of Thalictrum bouffordii (previously misidentified as T. javanicum). A. China, Sichuan, Luding, G.H. Xu 26353 (CDBI0026149). B. China, Sichuan, Shimian, C.C. Hsieh 41833 (SZ00092301). C. China, Sichuan, Tianquan, H.L. Tsiang 35238 (NAS00187277). D. China, Sichuan, Tianquan, H.L. Tsiang 35238 (PE00470992) (inset a: carpels; inset b: aggregate fruit).

FIGURE 2. Holotype sheet of Thalictrum bouffordii.

FIGURE 3. Thalictrum bouffordii in the wild (Tianquan in Sichuan, 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. Portion of rachis. H. Flower, with the sepals having fallen. I. Sepals (abaxial side). J. Stamens. K. Carpels. L. Aggregate fruit (immature). M. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 4. Thalictrum bouffordii in the wild (Luding in Sichuan, China).A. Habitat. B. Habit. C. Roots. D. Leaf (left: adaxial side; right: abaxial side). E. Leaflet (above: adaxial side; below: abaxial side). F. Flower, with the sepals having fallen. G. Sepals (abaxial side). H. Stamens. I. Carpels. Photographed by Y.P. Zeng.

FIGURE 5. Distribution of Thalictrum bouffordii (▲) and T. xinningense (■). Arrow indicates the type locality of T. bouffordii, i.e. Tianquan county in western Sichuan, China.

FIGURE 6. Holotype sheet of Thalictrum xinningense.

FIGURE 7. Thalictrum xinningense in the wild (Xinning in Hunan, China, the type locality). A. Habitat. B. Habit. C. Roots. D. Portion of stem. E. Portion of leaf. F. Portion of abaxial side of leaflet. G. Portion of rachis. H. Flower, with the sepals having fallen. I. Sepal (left: adaxial side; right: abaxial side). J. Stamens. K. Carpels. L. Aggregate fruit (immature). M. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 8. Specimens of Thalictrum xinningense from the type locality.A, B. China, Hunan, Xinning, Y.P. Zeng & Y.F. Luo 82 (IBSC).