China • Guizhou Province, Tongzi County, Guancang Town, Xianrenshan Mountain, elev. 1,200–1,300 m, growing on slopes beneath forests in karst areas, 27 April 2020, Chong-Bo Ma ZRB1607 (fl.) (holotype: ZY!; isotype: PE!), • 5 May 2024, Ren-Bo Zhang ZRB2661 (fl.) (paratype: ZY!, SCFI!), • 25 May 2024, Ren-Bo Zhang ZRB2676 (fr.) (paratype: ZY!).

Resembles S. changii in the subscapigerous habit, ovate-oblong and pinnately veined leaf lamina, and simple to compound terminal corymbs, but differs by membranous leaf lamina (vs. papery), 8–10 lateral veins (vs. 10–18), and stems and leaves pubescent with 2–5 mm long, uniseriate, spreading hairs (vs. sparsely white arachnoid to densely white tomentose) (Table 1).

Figure 1. 

Line drawing of Sinosenecio tongziensis A habit B a disk floret C a ray floret D top view of a capitulum E involucre F stamens. All from Chong-Bo Ma ZRB1607 (PE, ZY). Drawn by Tan Deng.

Herbs , scapigerous. Fresh rhizomes 6–16 mm in diam., clad in persistent brown petiole bases. Stems 1 to 3, erect, scapiform, 15–40 cm tall, ribbed, villous with 2–5 mm long, uniseriate, spreading hairs. Leaves several, radical, rosulate, densely villous as the stems; petiole 3–9 cm long; blade (broadly) ovate, obovate, or ovate-oblong, 4–14 × 3–10 cm, membranous, villous, densely so along veins, pinnately veined, lateral veins 4–5 pairs, base cordate, margin repand with mucronulate teeth, long ciliate. Capitula 4–29, arranged in terminal simple to compound corymbs; peduncles 1–5 cm long, slender, (sparsely) pubescent, with 3–20 mm long, linear or linear-spatulate bracts. Involucres campanulate, 4–7 × 4–7 mm, not calyculate; phyllaries ca. 13, lanceolate, oblanceolate or subelliptic, 4–6 × 1–1.6 mm, herbaceous with membranous margins, abaxially pubescent with uniseriate, spreading hairs, apically acuminate, ciliate at the apex and on upper margin. Ray florets 10–13; corolla tube 2.5–3.5 mm long, glabrous; ray yellow, oblong, 7–10 × 1.2–2.2 mm, 4-veined, apically 3-denticulate. Disk florets many; corolla yellow, 4–6 mm long, with 2–3 mm tube and campanulate limb; lobes ovate-lanceolate, ca. 0.8 mm long, apically acute. Anthers oblong, ca. 1.1 mm long, base obtuse to rounded, appendages lanceolate. Styles ca. 2.5 mm long in ray florets and 4–4.5 mm long in disk florets, branches recurved, ca. 0.8 mm long. Achenes cylindric, 1.6–2.0 mm long, inconspicuously ridged, glabrous. Pappus capillary-form, uniform, white, persistent, 2.4–4.0 mm long.

Figure 2. 

Sinosenecio tongziensis A habitat B habit C rhizome and fibrous roots D close-up of a petiole E adaxial (left) and abaxial (right) leaf surface F inflorescence (Photographed by Ying Liu and R.B. Zhang).

The filament collar of S. tongziensis consisted of uniformly sized cells (Fig. 3E), and the anther endothecial cell wall thickenings were polarized and radial (Fig. 3F), lending strong support for the phylogenetic affiliation of S. tongziensis in subtribe Tephroseridinae (see below).

Figure 3. 

Capitulum, florets, achenes, and floral micromorphological characters of Sinosenecio tongziensis A side view of a capitulum B longitudinal section of a capitulum C from left to right, a ray floret, two disc florets, and abaxial surface of a phyllary D achenes E uniformly-sized cells of filament collar F polarized and radial anther endothecial cell wall thickenings (Photographed by Ying Liu and R.B. Zhang).

Flowering from April to May, fruiting from May to June.

The specific epithet is derived from the type locality, Tongzi County, Guizhou Province, China.

The proposed Chinese name is “桐梓蒲儿根”, pronounced as “tóng zǐ pú ér gēn”.

The new species is endemic to Guizhou Province and is currently known only from the type locality, Xianrenshan Mountain, Tongzi County. It grows on slopes beneath the forests in karst areas at elevations of 1,200–1,300 m.

Sinosenecio tongziensis is currently recorded only at the type locality. Thousands of individuals are scattered across the mid-slope and at the base of the mountain, with approximately 600 to 700 mature individuals. Given its narrow distribution and relatively low number of mature plants, S. tongziensis may be more appropriately categorized as vulnerable (VU) according to the IUCN Red List Categories and Criteria (IUCN Standards and Petitions Committee 2022).

In the phylogenetic tree, Nemosenecio and Tephroseris were resolved as monophyletic (Fig. 4). Together with some species of Sinosenecio, these genera constituted a well-resolved clade representing subtribe Tephroseridinae (Fig. 4), conforming to previous studies (Wang et al. 2009; Ren et al. 2017; Zou et al. 2020). Despite its close resemblance to S. changii, S. tongziensis instead formed a weakly supported lineage (PP = 0.6) with S. bodinieri (Vaniot) B. Nordenstam, S. confervifer (H. Léveillé) Y. Liu & Q. E. Yang, S. nanchuanicus Z. Y. Liu, Y. Liu & Q. E. Yang, and S. globiger var. adenophyllus C.Jeffrey & Y.L.Chen (Fig. 4). It can be easily distinguished from these related species by the pinnately veined leaves (vs. palmately).

Figure 4. 

Bayesian phylogenetic tree based on ITS sequence data, showing the phylogenetic position of Sinosenecio tongziensis. Numbers at the nodes are Bayesian posterior probabilities. Nemosenecio and Tephroseris are highlighted in green and yellow, while S. tongziensis and S. changii are noted in red and blue respectively. GenBank accession numbers were provided for three accessions of S. changii.