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

Zeng, You-Pai, Fei, Wen-Qun, Yuan, Qiong & Yang, Qin-Er, 2021, Thalictrum changii (Ranunculaceae), a new species from southern Xizang (Tibet), China, Phytotaxa 511 (3), pp. 248-260 : 250-255

Thalictrum changii Y. P. Zeng, Q. Yuan & Q. E. Yang , sp. nov., Figs. 1–4

Type:— CHINA. Xizang: Cona county, near Lemen town , 27°49′41.74″N, 91°43′43.71″E, 2910 m, on moist cliffs in ravine, 20 August 2019, L . Wang , X. Q . Guo & Y. P . Zeng 3160 (holotype IBSC; isotypes IBSC, KUN, PE) .

Description:—Perennial herbs. Roots fibrous. Stem to 60 cm tall, branched, proximally glabrescent, distally glandularpubescent. Leaves 2–3-ternate; blade triangular, 5–20 cm long, 4–18 cm broad; leaflets ovate, broadly ovate or orbicular, 1–2.5 cm long, 0.8–2.5 cm broad, subcoriaceous, both sides glandular-pubescent, 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 paniculate-corymbiform; rachis glandular-pubescent. Pedicels ca. 2 cm long, densely glandularpubescent. Flowers bisexual, erect. Sepals 4, persistent at anthesis, cymbiform, narrowly elliptic, ca. 5 mm long, ca. 2 mm broad, white tinged faintly with greenish in the upper part, abaxially glandular-pubescent. Stamens ca. 25, ca. 5 mm long; filaments clavate, ca. 3.8 mm long, white; anthers oblong, ca. 1.2 mm long, ca. 0.5 mm broad, apex obtuse, white. Carpels 15–25, sessile, ca. 3 mm long; ovary lunate-fusiform, shallowly ribbed, ca. 1.5 mm long, glandularpubescent; style ca. 1.5 mm long, slightly curved at apex; stigma conspicuous, linear, ca. 0.5 mm long. Achenes sessile, ca. 4 mm long; body fusiform, ribbed, glandular-pubescent; style persistent, recurved at apex.

Distribution and habitat:— Thalictrum changii is currently known only from its type locality, i.e. Cona county in southern Xizang, China ( Fig. 5 ). It was found growing together with T. virgatum Hooker & Thomson (1855: 14) , a species remarkably distinct from it and widely distributed in the Sino-Himalayan region, in the same community on moist cliffs in a ravine at an altitude of 2910 m above the sea level.

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

Etymology:—We name our new species in honor of the late Professor Chao-chien Chang (1900–1972), former Deputy Director of the South China Institute of Botany (now known as South China Botanical Garden), Chinese Academy of Sciences (1955–1972), a renowned plant taxonomist who has made a significant contribution in understanding the taxonomy of the Chinese Asteraceae , Ranunculaceae and Violaceae .

Additional specimens examined:— CHINA. Xizang: Cona, W.Q. Fei 116 (IBSC).

Conservation status:— Thalictrum changii is currently known only from Cona county in southern Xizang, China, an area not fully botanized. The population we discovered consists of no more than 50 individuals. More populations are expected to be discovered. The conservation status of T. changii should be considered as “Data Deficient (DD)” before adequate information of this species is acquired ( IUCN Standards and Petitions Committee 2019).

Notes:— Thalictrum changii is most closely similar to T. yunnanense ( Figs. 6–8 ) in habit and in having 2–3- ternate leaves, paniculate-corymbiform inflorescence, clavate filaments, sessile, fusiform achenes, and particularly, in having glandular-pubescent stem (distal part), leaves, inflorescence rachis, pedicels and achenes, but differs by having subcoriaceous (vs. papery) leaflets, narrowly elliptic (vs. suborbicular), longer (ca. 5 mm vs. ca. 3.5 mm) and persistent (vs. caducous) sepals ( Figs. 4H , 8H ), and longer (ca. 3 mm vs. ca. 1.5 mm) carpels with longer (ca. 1.5 mm vs. 0.5 mm) styles ( Figs. 4J , 8J ). Geographically T. changii occurs in southern Xizang, whereas T. yunnanense occurs in Yunnan ( Wang 1994, 2000, 2018, Fu & Zhu 2001), with the type variety, var. yunnanense , in central Yunnan (Kunming city) and var. austroyunnanense Qian (1997: 262) in southern Yunnan (Lancang county) ( Qian 1997, Wang 2000, 2018, Fu & Zhu 2001), both distant from the new species in distribution ( Fig. 3 ).

Wang (1994) described Thalictrum yunnanense based on four collections from Yunnan, China. These include T.N. Liou 16668 (IBSC, KUN, PE), T.N. Liou 19727 (PE) and K.K. Tsoong 2140 (PE, PEY) all from Kunming in central Yunnan and K.K. Tsoong 2466 (PE, PEY) from Binchuan county in northwestern Yunnan, with the PE sheet of the first collection designated as the holotype ( Fig. 6 ). In the protologue, the author stated that all these collections had been previously misidentified as T. scabrifolium Franchet (1886: 369) , a species described from Heqing county in northwestern Yunnan, and that the description of T. scabrifolium given by Wang & Wang (1979) was based on those specimens just mentioned above. According to the protologue, T. yunnanense is closely similar to T. scabrifolium , but differs by having shorter stems, smaller (1.3–2.2 cm long, 1.5–2.8 cm broad), usually deltoid-ovate or broadly rhombic, rarely suborbicular terminal leaflets, 7 basal nerves of terminal leaflets, and apically slightly apiculate anthers. Wang (2018), however, described the anthers of T. yunnanense var. yunnanense as obtuse at apex. Our careful observations on the type specimens and living plants of T. yunnanense var. yunnanense ( Figs. 6–8 ) and T. scabrifolium ( Figs. 9 , 10 ) from their type localities reveal that the anthers are indeed apiculate in T. yunnanense var. yunnanense ( Fig. 8I ) and that T. yunnanense var. yunnanense is distinguishable from T. scabrifolium by having distinctly (vs. indistinctly) 3-lobate leaflets with remotely 2- or 3-denticulate (vs. densely more than 5-denticulate) lobes ( Figs. 8D , 10F ), suborbicular (vs. elliptic) sepals ( Figs. 8H , 10J ), and white (vs. purplish) filaments ( Figs. 8I , 10K ). As shown in Figure 11 , K.K. Tsoong 2466 from Binchuan county in northwestern Yunnan, a paratype collection of T. yunnanense var. yunnanense , actually agrees well with T. scabrifolium in all diagnostic characters and thus should belong to this species. Our thorough survey of Thalictrum specimens at major Chinese herbaria, including CDBI, HNWP, IBSC, KUN, NAS, PE, SM, SZ and WUK, indicates that T. scabrifolium is distributed only in Binchuan and Heqing counties in northwestern Yunnan, whereas T. yunnanense var. yunnanense occurs only in Kunming city in central Yunnan and T. yunnanense var. austroyunnanense is currently known only from its type locality, i.e. Lancang county in southern Yunnan ( Fig. 5 ).

In the protologue of Thalictrum yunnanense var. austroyunnanense, Qian (1997) stated that this variety differed from its type variety, var. yunnanense , by having longer styles (0.8–1.3 mm long). Wang (2000) recognized this variety as an independent entity, stating that it was distinguishable from the type variety by having straight, only apically uncinate styles and broadly rhombic or suborbicular leaflets up to 2.9 cm long, 4 cm broad. In his monograph of the Chinese Thalictrum, Wang (2018) pointed out further that T. yunnanense var. austroyunnanense differed from the type variety by having narrowly oblong anthers and fusiform achenes with longer persistent style (1.5 mm long). Upon a critical examination of the type material of T. yunnanense var. austroyunnanense ( Fig. 12 ), we found that this taxon is also readily distinguishable from its type variety by having terminal leaflets broadly obovate (vs. suborbicular) and indistinctly (vs. distinctly) 3-lobate with crenate (vs. denticulate) lobes, flowers purplish (vs. whitish green), styles 0.8–1.3 mm (vs. ca. 0.7 mm) long, achenes narrowly fusiform (vs. fusiform). From our new species T. changii , T. yunnanense var. austroyunnanense differs by having indistinctly (vs. distinctly) 3-lobate leaflets, purplish (vs. white) flowers, and narrowly fusiform (vs. fusiform) achenes. Indeed, judging from the morphological characters and geographical distribution, it seems better to treat T. yunnanense var. austroyunnanense as an independent species of its own. We will deal with this problem elsewhere.

In order to facilitate the identification of Thalictrum changii and its closely allied taxa, an identification key to them is provided below.

Figures

FIGURE 1. Holotype sheet of Thalictrum changii.

FIGURE 2. Isotype sheets of Thalictrum changii.

FIGURE 3. Thalictrumchangii inthe wild(Cona county in southernXizang,China,the type locality).A.Habitat.B, C.Habit.Photographed by Y.P. Zeng.

FIGURE 4. Thalictrum changii in the wild (Cona county in southern Xizang, China, the type locality). A. Roots. B. Portion of stem. C. Leaf (above: adaxial side; below: abaxial side). D. Terminal leaflet (above: adaxial side; below: abaxial side). E. Portion of a terminal leaflet (adaxial side), showing the glandular hairs. F. Portion of a terminal leaflet (abaxial side), showing the glandular hairs. G. Flower. H. Sepals (abaxial side). I. Stamens. J. Carpels. K. Aggregate fruit (immature). L. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 5. Distribution of Thalictrum changii (●), T. scabrifolium (▲), T. yunnanense var. austroyunnanense (♦) and T. yunnanense var. yunnanense (■).

FIGURE 6. Holotype sheet of Thalictrum yunnanense var. yunnanense.

FIGURE 7. Thalictrum yunnanense var. yunnanense in the wild (Kunming in central Yunnan, China, the type locality).A. Habitat. B, C. Habit. Photographed by Y.P. Zeng.

FIGURE 8. Thalictrum yunnanense var. yunnanense in the wild (Kunming in central Yunnan, China, the type locality). A. Roots. B. Portion of stem. C. Leaf (above: adaxial side; below: abaxial side). D. Terminal leaflet (above: adaxial side; below: abaxial side). E. Portion of a terminal leaflet (adaxial side), showing the glandular hairs. F. Portion of a terminal leaflet (abaxial side), showing the glandular hairs. G. Flower, with the sepals having fallen. H. Sepal (left: adaxial side; right: abaxial side). I. Stamens. J. Carpels. K. Aggregate fruit (immature). L. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 9. A type specimen of Thalictrum scabrifolium.

FIGURE 10. Thalictrum scabrifolium in the wild (Heqing county in northwestern Yunnan, China, the type locality).A. Habitat. B. Habit. C. Roots. D. Portion of stem. E. Leaf (abaxial side). F. Terminal leaflet (adaxial side). G. Portion of a terminal leaflet (adaxial side), showing the glandular hairs. H. Portion of a terminal leaflet (abaxial side), showing the glandular hairs. I. Flower, with the sepals having fallen. J. Sepal (left: adaxial side; right: abaxial side). K. Stamens. L. Carpels. M. Aggregate fruit (immature). N. Achenes (immature). Photographed by Y.P. Zeng.

FIGURE 11. Thalictrum scabrifolium, K.K. Tsoong 2466, Binchuan county, northwestern Yunnan, China. A. PEY sheet (barcode PEY0003110). B, C. PE sheets (barcode PE00450033 and barcode PE00450034, respectively), cited as paratypes of T. yunnanense. D. Portion of a leaflet (abaxial side) from the PE00450033 sheet. E. Flower from the PE00450033 sheet, with the sepals having fallen. F. Portion of a leaflet (abaxial side) from the PE00450034 sheet. G. Flower from the PE00450034 sheet, with the sepals having fallen.

FIGURE 12. Holotype sheet of Thalictrum yunnanense var. austroyunnanense (inset a: portion of a flower, showing stamens and carpels; inset b: aggregate fruit).