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Systematic position of the enigmatic genus Sheareria ( Asteraceae)—evidence from molecular, morphological and cytological data
Author(s) -
Gao Tian-Gang,
Wang Wei,
Bayer Randall J.,
Li De-Zhu
Publication year - 2009
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.1002/tax.583007
Subject(s) - biology , clade , achene , asteraceae , tribe , botany , genus , evolutionary biology , phylogenetic tree , biochemistry , sociology , gene , anthropology
The systematic position of the monoecious rheophyte, Sheareria (Asteraceae), a genus endemic to China, has been long disputed and never rigorously examined. In this study, two molecular datasets ( trnL‐F, ITS ), plus morphological and cytological characters, were used to assess the systematic position of Sheareria. The broader phylogenetic analyses based on the trnL‐F data placed Sheareria in the tribe Astereae with strong support. This placement was also supported by the lanceolate style, “Asteroid type” ligule epidermis, yellow anthers, green achenes, and basic chromosome number of x = 9. Analysis of the tribe Astereae based on the ITS dataset showed that Sheareria and three East Asian genera ( Kalimeris, Aster, Rhynchospermum ) formed a strongly supported clade characterized by flat, 2‐ribbed, glandular disc achenes. Detailed morphological comparisons indicate that Sheareria is more similar to Kalimeris than to Rhynchospermum . Within this clade, Sheareria is distinguished from other genera by its monoecious breeding system (vs. gynomonoecious). Based on fossil and geological evidence, the development of monoecy in Sheareria is discussed. Within Sheareria, only one species, S. nana , is recognized; S. leshanensis , a newly described species, is placed in synonymy.