Sinosenecio jiuzhaigouensi s B. Chen, Ying Liu & Q.E. Yang

Chen, Bin, Liu, Ying, Luo, Jian-Xun, Wang, Qi & Yang, Qin-Er, 2022, Sinosenecio jiuzhaigouensis (Asteraceae, Senecioneae), a new species from Sichuan, China, Phytotaxa 544 (3), pp. 289-294 : 289-293

Sinosenecio jiuzhaigouensi s B. Chen, Ying Liu & Q.E. Yang , sp. nov., Figs. 1 , 2 .

Type:— CHINA. Sichuan: Jiuzhaigou county, Anle town , on rocky slopes along Baihe riverbank, alt. 1570 m, 5 October 2018, Bin Chen CB07115 (holotype CSH, barcode CSH0180125 ; isotypes CSH, IBSC, barcodes CSH0178474 , CSH0189306 , IBSC0868149 , IBSC0868150 ). Fig. 2 .

Diagnosis:— Sinosenecio jiuzhaigouensis resembles S. hederifolius ( Dümmer 1912: 482) Nordenstam (1978: 50) and S. cyclaminifolius (Franchet 1894: 362) Nordenstam (1978: 50) in having ovate-cordate leaf blade and solitary capitula, but differs by having swollen (vs. not swollen) rhizomes and smaller capitula (2–3 vs. 4–5 cm in diameter).

Description:—Scapigerous herbs. Rhizomes transverse or descending, swollen, tuberous, 3–6 cm long. Stems solitary, erect, scapiform, 7–23 cm tall, white tomentose, simple. Leaves radical; petiole 1–8 cm long, initially densely but later sparsely white tomentose; blade ovate, ovate-cordate, or ovate-suborbicular, 1.5–5 cm × 1–4 cm, ± thickly papery, abaxially pale green to purplish, sparsely white tomentose or glabrescent, adaxially green, sparsely white tomentose or glabrescent, palmately 3–5-veined, margin entire, base cordate, rarely truncate, apex rounded. Capitula solitary, terminal, 2–3 cm in diameter, scape with 1 or 2 linear-lanceolate bracteoles in middle or lower part. Involucres campanulate, 8 × 6–7 mm, not calyculate; phyllaries 13–15, linear-oblong, 6–7 × 1.5–2.5 mm, white tomentose, ± glabrescent, margin scarious, apically acute, fimbriate-ciliate, sometimes purplish. Ray florets ca. 13; corolla tube 2–2.5 mm long; lamina 12 × 2.5 mm long, yellow, oblong or oblanceolate-oblong, 4-veined, apically 3-denticulate, obtuse to rounded. Disk florets numerous; corolla yellow, 4–4.5 mm long, with ca. 3 mm long corolla tube; lobes ovate, 1–1.5 mm long, apically acute. Anthers oblong, ca. 1.5 mm long, basally obtuse to rounded, appendages ovatelanceolate. Style branches ca. 0.7 mm long, truncate, papillose. Achenes cylindric, 2–3 mm long, smooth, glabrous. Pappus white, 2–3 mm long.

Floral micromorphological characters, achene surface feature, and chromosome number:—The filament collar of the new species consists of uniformly sized cells ( Fig. 3A ), and the anther endothecial cell wall thickenings are polar ( Fig. 3B ). The achene is glabrous and smooth ( Fig. 3C ). The chromosome number is 2 n = 60 ( Fig. 3D ).

Distribution and habitat:— Sinosenecio jiuzhaigouensis is currently known only from its type locality, i.e. Jiuzhaigou county in northwestern Sichuan province, China ( Fig. 4 ). It grows on steep rocky slopes along riverbank at an elevation of ca. 1570 m.

Phenology:—Flowering late April to May; fruiting June.

Etymology:—The specific epithet, “ jiuzhaigouensis ”, refers to the type locality of the new species, i.e. Jiuzhaigou county in northwestern Sichuan province, China.

Conservation status: The only known population of Sinosenecio jiuzhaigouensis at the type locality comprises ca. 80 individuals within an area of 100 m 2. According to the IUCN Red List Categories and Criteria (IUCN, 2012), the new species should be considered critically endangered (CR).

Notes:— Sinosenecio , as is defined by Chen et al. (2011), contains two species assemblages with different configurations of anther endothecial cell wall thickenings (polar and radial vs. strictly polar), chromosome numbers (2 n = 48 vs. 2 n = 60), and geographic distribution (central and southern China vs. areas around the Sichuan basin in southwestern China) (Liu 2010, Liu & Yang 2011a, b, 2012). Sinosenecio jiuzhaigouensis should be a member of the latter assemblage based on its strictly polar anther endothecial cell wall thickenings, chromosome number of 2 n = 60, and its geographical distribution in Jiuzhaigou county at the northern margin of the Sichuan basin. Among species of this assemblage, S. jiuzhaigouensis most closely resembles S. hederifolius in having ovate-cordate leaf blade, solitary capitula, and habitat preference (rocky cliffs), but differs by having swollen (vs. not swollen) rhizomes, abaxially sparsely white tomentose or glabrescent (vs. fulvous tomentose) leaf blade, and smaller capitula (2–3 vs. 4–5 cm in diameter). Interestingly, we found that these two species grew on rocky cliffs along the Baihe river in Jiuzhaigou county, but in different microhabitats. Sinosenecio jiuzhaigouensis was restricted on open and moist rocky cliffs at the entrance of a lush ravine, whereas S. hederifolius was discovered only in bushes on dry rocky cliffs. Although both species entered their flowering season in April, no morphologically putative hybrids were observed in the wild probably due to isolation by microhabitat preference or intrinsic postzygotic barriers. Sinosenecio jiuzhaigouensis also resembles S. cyclaminifolius in leaf shape and in having solitary capitula, but differs by having swollen (vs. not swollen) rhizomes, abaxially sparsely white tomentose or glabrescent (vs. densely white lanate) leaf blade, smaller capitula (2–3 vs. 4–5 cm in diameter), and persistent (vs. deciduous) pappus. Geographically, S. jiuzhaigouensis is currently known only from Jiuzhaigou county in northwestern Sichuan, whereas S. cyclaminifolius is distributed in eastern Sichuan and northern Chongqing.

To facilitate the identification of Sinosenecio jiuzhaigouensis and its two putative closest species, an identification key is provided.

Figures

FIGURE 1. Sinosenecio jiuzhaigouensis. A. Habitat. B. Plants in vegetative period, not flowering. C. An individual in vegetative period, showing the rhizome. D. Leaves (left: adaxial side; right: abaxial side). E.A flowering individual in cultivation. F. Capitulum (longitudinal section). G. Phyllaries. H. Ray floret. I. Disk florets. Voucher: Bin Chen CB07115 (CSH, IBSC).

FIGURE 2. Holotype (A) and isotype (B) sheets of Sinosenecio jiuzhaigouensis.

FIGURE 3. Floral micromorphological characters, achene surface, and mitotic metaphase chromosomes of Sinosenecio jiuzhaigouensis. A. Uniformly sized cells of filament collar. B. Polar endothecial cell wall thickenings. C. Smooth achene surface. D. Mitotic metaphase chromosomes (2n = 60). Voucher: Bin Chen CB07115 (CSH, IBSC).

FIGURE 4. Distribution of Sinosenecio jiuzhaigouensis (●).