Homostylium polium (Schneid.) Z. X. Fu, 2025

Chen, Xinyu & Fu, Zhixi, 2025, Resurrection of the genus Homostylium Nees for the former Aster ser. Albescentes Y. Ling (Astereae, Asteraceae), with an updated generic synopsis, PhytoKeys 259, pp. 27-66 : 27-66

7. Homostylium polium (Schneid.) Z. X. Fu comb. nov.

Figs 17 , 18 , 19

≡ Aster polius C. K. Schneid. , Pl. Wilson. (Sargent) 3: 459. 1917. ≡ Sinosidus polius (C. K. Schneid.) G. L. Nesom , Phytoneuron 2020-64: 14. 2020. Type: China, Sichuan, Xiaojin (= Nin Monkong Ting), head of Chin Ho Valley, alt. 7000–9000 ft, June 1908, E. H. Wilson 2233 (holotype, A 00003825!; isotype, US 01696632!) (Suppl. material 1: figs S 39, S 40).

Type.

China • Sichuan, Xiaojin (= Nin Monkong Ting), head of Chin Ho Valley , alt. 7000–9000 ft, June 1908, E. H. Wilson 2233 (holotype, A 00003825 !; isotype, US 01696632 !) (Suppl. material 1: figs S 39, S 40) .

Description.

Shrubs, 56–118 cm tall. Leaves subleathery, alternate, narrowly ovate to elliptic, 1.3–3.7 × 0.4–1.6 cm, margin entire, strongly revolute, adaxially green, scabridulous, verrucose-pubescent, abaxially densely white tomentose or arachnoid, including the midrib. Capitula 1.5 cm in diameter, radiate, numerous, 3–10 (- 20), in corymbiform synflorescences, terminal on current-year lateral branches. Peduncles slender, 5–10 mm long. Involucres campanulate or broadly campanulate, 5–6 × 5–7 mm. Phyllaries 4–5 - seriate, imbricate, outer phyllaries ovate, ca. 1.2 mm long, narrowly lanceolate, inner phyllaries unequal, lanceolate, 3–4 × ca. 1 mm.

Distribution.

Endemic to China, Sichuan, Xiaojin (Fig. 18 ).

Habitat.

Shrubland of arid river valleys. 2000–2700 m.

Phenology.

Flowering and Fruiting ca. July to September.

Etymology.

The specific epithet “ polium ” is derived from the Greek “ polios ”, meaning “ gray ” or “ hoary ”, combined with the Latin neuter suffix “ - um ”. The name likely refers to the grayish indumentum on the stems or the adaxial leaf surface.

Specimens examined.

China • Sichuan: Xiaojin , Z. X. Fu 2918 ( PE), 2919 ( PE), 2920 ( PE), 2921 ( PE), 2922 ( PE), 2923 ( PE), 2924 ( PE), 2925 ( PE), 2927 ( PE) , E. H. Wilson 2233 ( A 00003825 , US 01696632 ) .

Notes.

Xiaojin County is located at the junction of the China-Japan Forest Subregion and the China-Himalayan Plant Subregion, resulting in a diverse vegetation composition. Compared to surrounding areas, the county faces harsh environmental conditions, characterized by water scarcity and aridity. A distinctive feature of the region is the widespread presence of mesophotic, drought-tolerant sparse shrub vegetation. It also underscores the restricted distribution of H. polium . Based on combined ITS and ETS data, Fu et al. (2019) reconstructed a BI phylogenetic tree for Aster , including five Homostylium species. The results showed that H. polium is more closely related to H. argyropholium , compared to H. lavandulifolium . These three species, together with H. albescens and H. fulgidulum , cluster into a monophyletic clade, with H. fulgidulum positioned as the basal species.

Figures

Figure 17. Homostylium polium (Schneid.) Z. X. Fu. A. Habit; B. Habitat; C. Capitula (lateral view, showing the involucre); D. Abaxial surface of leaves; E. Capitula; F. Branches of stem (showing capitula terminal on lateral branches). Photographed by Z. X. Fu from Z. X. Fu 2918 (PE).

Figure 18. Distribution of Homostylium polium. China is centrally located on the map.

Figure 19. Homostylium polium (Schneid.) Z. X. Fu. A. Habit; B. Capitulum; C. Involucral bracts; D. Ray floret; E. Style branches of ray floret; F. Disc floret; G. Style branches of disc floret; H. Stamen of disc floret; I. Pappus bristle. Drawn by Z. J. Chen.