Leaf morphology and anatomy of Schlechtendalia luzulifolia, a basal member of subfamily Barnadesioideae (Asteraceae).

The article focuses on the molecular phylogeny, morphology, and leaf anatomy of the subfamily Barnadesioideae within the Asteraceae family, emphasizing the basal and monotypic genus Schlechtendalia. Barnadesioideae comprises 10 genera and 87 species primarily distributed in South America, with Schlechtendalia luzulifolia uniquely adapted to mesic environments in Uruguay, southern Brazil, and northeastern Argentina. Phylogenetic analyses confirm Schlechtendalia as the sister genus to the rest of the subfamily, distinguished by its atypical monocot-like leaf morphology and anatomy, including parallel venation, amphistomatic leaves, and distinctive trichomes. The study highlights ecological correlations of leaf traits across Barnadesioideae genera, linking anatomical features to adaptations in mesic, semi-xeric, and xeric habitats, and discusses Schlechtendalia’s evolutionary significance as a diploid lineage potentially adapted to mesic environments before the Andean uplift and aridification of South America.