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| Grindelia mutabilis Fern.Fern. & G.Heiden, in Fernandes, de Souza, Iganci, de Souza-Chies et Heiden, 2026. Illustration by João Iganci. photos by F. Fernandes, B. de Souza and M. Grings. |
Abstract
Grindelia mutabilis (Asteraceae, Astereae), a new species from Brazil endemic to the Espinal Ecoregion of the Río de La Plata Grasslands Bioregion and Pampa Province of the Chaco Biogeographical Domain, is proposed and illustrated. The new species is characterized by a combination of traits: small, rosette cespitose habit, linear to linear–oblanceolate leaves, light-yellow to pastel salmon ray florets, three-winged ray floret cypselae bearing a pappus of two to four elements and two-winged disc floret cypselae bearing a pappus of two elements. It has a highly restricted habitat and is known exclusively within Parque Estadual do Espinilho in Rio Grande do Sul, Brazil. Preliminary conservation assessments classify the new species as Critically Endangered. We provide illustrations and photographs, as well as a distribution map with an identification key for the South American Grindelia species with winged cypselae. The intriguing morphology of this species combines characters traditionally regarded as diagnostic for Notopappus, a genus segregated from Haplopappus and Grindelia. Previously published phylogenetic studies of related taxa indicate that the recognition of Notopappus as monophyletic is not supported and render Grindelia as non-monophyletic too. Based on this combined morphological evidence and existing phylogenetic hypotheses, we reaffirm the non-monophyly of Notopappus and formally propose its synonymization under Grindelia s.l.
Keywords: Asteroideae; Compositae; endangered species; endemism; grassland; Machaerantherinae; savanna; taxonomy
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| Grindelia mutabilis (Asteraceae). (A) Habitat on sandy, halophilous soils within the Espinal/Ñandubay savanna of Espinilho State Park, Barra do Quaraí, Rio Grande do Sul, Brazil. (B) Cespitose rosette habit with spreading branches. (C) Leaves. (D) Lateral view of the capitulum. (E) Capitulum with pastel-salmon ray florets. (F) Capitulum with light-yellow ray florets. Pictures by F. Fernandes (A), B. de Souza (B–D, F), and M. Grings (E). |
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| Grindelia mutabilis (Asteraceae). (A) Habitat. (B) Cespitose rosette habit with spreading branches; scale bar = 0.3 m. (C) Leaves and bracts, from left to right: leaf, bract distant from the capitulum, and bract closest to the capitulum; scale bar = 20 mm. (D) Phyllaries, from left to right: outer, middle, and inner phyllaries; scale bar = 4 mm. (E) Frontal view of the capitulum showing ray florets with pastel salmon-colored ligules; scale bar = 10 mm. (F) Lateral view of the capitulum showing ray florets with light-yellow ligules; scale bar = 10 mm. (G) Ray floret; scale bar = 5 mm. (H) Disc floret; scale bar = 2 mm. (I) Pappus; scale bar = 2 mm. (J) Cypselae, from left to right: cypsela of a disc floret and cypsela of a ray floret; scale bar = 1 mm. Illustration by João Iganci. |
Grindelia mutabilis Fern.Fern. & G.Heiden, sp. nov.
Diagnosis: Grindelia mutabilis differs from all other species in the genus by the unique combination of cespitose rosette habit 0.2–0.3 m tall; leaves linear to linear–oblanceolate; ray corollas light yellow to pastel salmon; three-winged ray floret cypselae bearing a pappus of two to four elements and two-winged disc floret cypselae bearing a pappus of two elements.
Etymology: The specific epithet mutabilis (Latin for “changeable” or “variable”) refers to the ligules of the ray florets that change from light yellow to pastel salmon along the maturity.
Fernando Fernandes, Bruno de Souza, João Iganci, Tatiana Teixeira de Souza-Chies and Gustavo Heiden. 2026. Grindelia mutabilis (Asteraceae: Astereae), a New South American Species and a Link for synonymizing Notopappus. Plants. 15(5), 760. DOI: doi.org/10.3390/plants15050760