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Soroseris Stebb.

绢毛苣属

Description from Flora of China

Stebbinsia Lipschitz; Tibetoseris Sennikov.

Herbs, perennial, rosulate, often acaulescent, sometimes from a stout vertical subterranean rosette shoot with scalelike leaves (cataphylls) below leaf rosette or caulescent with a thick hollow stem. Leaves rosulate or along stem. Rosette shoot inflated at apex to a convex, hollow receptacle or rarely elongated to a hollow cylindric axis, carrying usually numerous, densely crowded capitula. Capitula with 4(or 5) or 15-30 florets; peduncle mostly shorter to rarely longer than involucre. Involucre narrowly cylindric or rarely campanulate. Phyllaries in few series; outer phyllaries mostly 2, linear, similar to uppermost leaves; inner phyllaries 4-15, ± lanceolate, subequal in length, connate or distinct in basal part, herbaceous at maturity. Receptacle naked. Florets yellow, sometimes basally blackish, more rarely white. Achene subcylindric, subfusiform, obcolumnar, or narrowly obconical, subcompressed, with 5 mostly rather slender and sometimes weak main ribs and 1-3(or 4) secondary often ± subequal ribs in between but otherwise smooth, inconspicuously or rarely apically conspicuously acutely papillate, apex ± truncate or rarely shortly beaked. Pappus whitish to straw-colored, often apically grayish, bristles stiff, coarse, scabrid, and usually ± caducous.

Cytological and molecular work by J. W. Zhang et al. (Bot. J. Linn. Soc. 154: 79-87. 2007; Taxon 60: 15-26. 2011) confirmed the very close relationship between the monotypic genus Stebbinsia (accommodating S. umbrella) and Soroseris, and supports its unification with the latter. Further evidence comes from the molecular phylogenetic analysis of subtribe Crepidinae by J. W. Zhang et al. (in prep.) revealing that Youngia depressa, recently separated for convincing morphological reasons from Youngia (see also there, p. 252) in a new genus Tibetoseris (Sennikov & I. D. Illarionova, Komarovia 5: 96. 2008), which subsequently was, similarly convincingly, most recently recircumscribed to become a monotypic genus for Y. depressa by D. Maity & Maiti (Compositae Newslett. 48: 22-42. 2010), actually is also nested in the clade of Soroseris. Soroseris depressa, in fact, well agrees morphologically; it strongly resembles S. umbrella in leaf shape and habit, while in the number of phyllaries it is intermediate between S. umbrella and the remainder of Soroseris. We therefore understand Soroseris in this wider sense, including both Stebbinsia and Tibetoseris s.s. As has been shown by J. W. Zhang et al. (Taxon 60: 15-26. 2011), speciation in Soroseris is rather recent, their relationship being not resolved in their molecular analyses. Also morphologically, distinction is not always easy, especially between S. glomerata and S. hookeriana, and more studies are needed.

About seven species: Bhutan, W China, N India, Kashmir, Nepal, Pakistan; seven species in China.

(Authors: Shi Zhu (石铸 Shih Chu); Norbert Kilian)


 

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