Leaf morphological variation of Brickellia section Barroetea (A. Gray) E.E. Schill. & R. Scott and related species

Background: The leaves have been used to define sections in the genus Brickellia, allowing us to postulate their taxonomic value in monophyletic groups, as well as to identify the degree of morphological similarity between species and sections in a taxonomic and phylogenetic context. Questions: The species of Brickellia section Barroetea can be differentiated by their leaf blade shapes?, do section Barroetea have leaf blades different from other sections of the genus?, do these leaf shapes represent a conserved trait in the genus? Studied species: Six species from the section Barroetea and 19 species from other sections of Brickellia and related genera (Ageratina and Carminatia) were analyzed. Methods: A linear discriminant analysis and a phylomorphospace analysis were performed to evaluate the conservation status of the leaf shape and to know their morphological differences. Results: Species of the section Barroetea showed significant differences at the specific level, except in Brickellia sonorana. Furthermore, the evaluated species of sections Barroetea, Brickellia, Coleosanthus, Leptanthodium, and Xerobrickellia tend to have ovate-deltoid shapes, except Microphyllae with reniform shapes, in Phanerostylis ovate or elliptical, and Gemmipedium and Kuhnia with linear shapes. The phylomorphospace reveals an overlap in the analyzed sections, where the ancestral sections show a greater morphological change than the recently diversified. The conservation of the leaf shape is not confirmed statistically. Conclusions: Most species of Brickellia section Barroetea can be differentiated between them, but not from the other sections of the genus Brickellia by the leaf’s shapes. The leaf shape of the genus is not conservated.