Sinosenecio minshanicus XiuJ.Su, W.Q.Fei, YingLiu & Q.E.Yang, 2023

Su, Xiu-Jiang, Fei, Wen-Qun, Zhao, Ding, Liu, Ying & Yang, Qin-Er, 2023, Sinosenecio minshanicus (Asteraceae, Senecioneae), a new species from south-eastern Gansu and northern Sichuan, China, PhytoKeys 218, pp. 79-91 : 79

publication ID	https://dx.doi.org/10.3897/phytokeys.218.97475
persistent identifier	https://treatment.plazi.org/id/F39CB994-AA17-55A9-879E-078FE31949B7
treatment provided by	PhytoKeys by Pensoft
scientific name	Sinosenecio minshanicus XiuJ.Su, W.Q.Fei, YingLiu & Q.E.Yang
status	sp. nov.

Treatment

Sinosenecio minshanicus XiuJ.Su, W.Q.Fei, YingLiu & Q.E.Yang sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 6 View Figure 6 and 7 View Figure 7

Type.

China. Sichuan province: Pingwu county, Huya town, Xuebaoding National Nature Reserve , on moist rocky cliff in valley, alt. ca. 2240 m, 6 June 2022, W.Q. Fei & J. Li 563 (holotype: IBSC; isotypes: CDBI, PE, SYS). Fig. 3 View Figure 3 .

Diagnosis.

Sinosenecio minshanicus most closely resembles S. rotundifolius in having a scapigerous habit, orbicular leaves and solitary capitula, but differs by the presence (vs. absence) of stolons and by having thinner rhizomes (ca. 2 mm vs. more than 5 mm in diameter), stems proximally sparsely fulvous arachnoid or glabrescent (vs. densely sericeous-villous) and obscure (vs. conspicuous) main veins on adaxial surface of leaves.

Description.

Scapigerous herbs with axillary slender stolons. Rhizomes short, ca. 2 mm in diameter, with few fibrous roots. Stems solitary, erect, purplish, scapiform, 7.5-17 cm tall, simple, proximally sparsely fulvous arachnoid or glabrescent, distally fulvous pubescent with uniseriate hairs or glabrescent. Leaves radical, rosulate; petioles 0.5-5 cm long, slender, basally expanded, pubescent with uniseriate hairs; blades orbicular or reniform-orbicular, 0.5-1.7 × 0.7-2.3 cm, subleathery, abaxially purplish, fulvous arachnoid, adaxially green, glabrous, palmately 5-veined, veins obscure adaxially and slightly raised abaxially, margin subentire or repand and mucronulate, base cordate, apex acute or rounded. Capitula terminal, solitary, radiating, 2.5-3.4 cm in diameter, scape with 1-3 linear bracts 2-5 mm long in middle or upper parts. Involucres long-campanulate, ca. 5 × 7-10 mm, ecalyculate, fulvous pubescent; phyllaries 10-14, oblong-lanceolate, 1-2 mm wide, margin narrowly scarious, apically purplish, fulvous pubescent. Ray florets 8-12; tube 3-3.5 mm long; lamina yellow, oblong, 10-14 × 2-3 mm, 4-veined, apically denticulate. Disc florets 15-32; corolla yellow, ca. 6 mm long, with ca. 2.5 mm long tube and funnel-form campanulate limb; lobes ovate-lanceolate, apically acuminate. Anthers oblong, 2.5 mm long, basally obtuse to rounded, appendages ovate-lanceolate; anther-collar cells uniform (Fig. 8A and B View Figure 8 ); endothecial cell wall thickenings strictly polar (Fig. 8C and D View Figure 8 ). Style branches 0.7 mm long, recurved, apically truncate, papillose. Achenes (immature) cylindrical, ca. 2 mm long, glabrous, smooth, ribbed (Fig. 8E and F View Figure 8 ). Pappus white, 4-6 mm long. 2 n = 60 (Fig. 9A and B View Figure 9 ).

Phenology.

Flowering in June; fruiting in July.

Etymology.

The specific epithet, " Sinosenecio minshanicus ", is derived from Min Shan, a chain of mountains extending from south-western Gansu to northern Sichuan, China. The currently known localities of the new species are all situated in the Minshan Mountains region.

Distribution.

Sinosenecio minshanicus is currently known from south-eastern Gansu (Wenxian and Zhugqu counties) and northern Sichuan (Pingwu county), China (Fig. 10 View Figure 10 ). It grows on shaded and moist places in forests or on rocky cliffs and slopes along stream sides at altitudes of 2200-3000 m above sea level.

Additional specimens examined.

China. Gansu province: Wenxian county, Baishuijiang Nature Reserve, Qiujiaba , on slope in forest, alt. 2500 m, 26 June 2006, Baishuijiang Exped. 0320 (PE); Wenxian county , Baishuijiang Nature Reserve , in Abies and Rhododendron forests, alt. 3000 m, 30 June 2006, Baishuijiang Exped. 0800 (PE); Zhugqu county , Chagang forestry station, in grasses and mosses on shaded rocky slopes, alt. ca. 2400 m, 21 June 2022, W. Q. Fei & J. Li 598 (IBSC, SYS) .

Conservation status.

Sinosenecio minshanicus is currently known from Wenxian and Zhugqu counties in south-eastern Gansu and Pingwu county in northern Sichuan, China. Only approximately 30 to 50 mature individuals were discovered each in the Pingwu and Zhugqu populations. They are scattered within ca. 1 km along a valley. Data of the size of the two Wenxian populations are not available. Although the known populations of S. minshanicus are all located within national nature reserves, some human activities, road building in particular, may destroy their habitats and, thus, severely affect the survival of this species. According to the IUCN Red List Categories and Criteria ( IUCN 2012), S. minshanicus may better be categorised as Endangered (EN).

Notes.

The genus Sinosenecio as defined by Chen et al. (2011) encompasses two major groups of species, with one having strictly polar anther endothecial cell wall thickenings and base chromosome number of x = 30 and occurring in mountainous areas largely surrounding the Sichuan basin in south-western China and the other having polar and radial thickenings and base chromosome number of x = 24 (rarely 13) and largely occurring in mountainous areas in central and southern China ( Liu 2010; Chen et al. 2011; Liu and Yang 2011a, b, 2012; Liu et al. 2019; Zou et al. 2020; Chen et al. 2022; Peng et al. 2022; Su et al. 2023). Obviously, S. minshanicus belongs to the first group, in which 15 species are currently recognised, including S. homogyniphyllus (Cumm.) B. Nord., the type species of Sinosenecio and S. rotundifolius , the putative closest ally of S. minshanicus ( Liu 2010; Chen et al. 2011; Chen et al. 2022; Su et al. 2023). In this group, S. minshanicus is the only species hitherto known to have slender stolons.

Sinosenecio rotundifolius was described on the basis of a single collection, Inst. Biol. Sichuan Exped. 702 (Fig. 4 View Figure 4 ), from Songpan county in northern Sichuan, China ( Chen 1988). It was recorded to be locally endemic to Songpan in the account of Sinosenecio in the "Flora Reipublicae Popularis Sinicae" ( Chen 1999). The results of our observation of living plants of this species from the type locality are shown in Fig. 5 View Figure 5 . As mentioned earlier, Liu (2010) cited two collections, Baishuijiang Exped. 0320 (PE) and Baishuijiang Exped. 0800 (PE), from Wenxian county in south-eastern Gansu under S. rotundifolius , thus extending the distributional range of this species. This treatment was adopted by Chen et al. (2011) in the account of Sinosenecio in the "Flora of China". We re-examined these two collections and found that they have slender stolons and match S. minshanicus well also in other characters and thus belong to this species. The previous record of S. rotundifolius from south-eastern Gansu actually refers to S. minshanicus . Currently S. rotundifolius is indeed known only from its type locality in Songpan county in northern Sichuan, not occurring in south-eastern Gansu. As pointed out by Jeffrey and Chen (1984), Sinosenecio is noteworthy for the narrow endemism of many of its species.

Sinosenecio minshanicus occurs in the same valley together with another species of the same group in the genus, i.e. S. pingwuensis Xiu J. Su et al. ( Su et al. 2023). Both of them prefer shaded and moist microhabitat and share the same flowering time (June). However, we did not observe any morphologically putative hybrids between them, which is probably due to isolation via intrinsic post-zygotic barriers.