Evolution of Stem and Leaf Structural Diversity: a Case Study in Lychnophorinae (Asteraceae)

Lychnophorinae occurs mainly in campos rupestres and cerrados of the Cerrado Domain (Brazil) and are species subject to fire occurrences and intense solar radiation, occupying acid and well-drained soils. Informative characters on the taxonomy of this subtribe were studied considering the leaf and stem morphology and anatomy. In addition, putative synapomorphies and features that probably determined the success of these species in occupying these habitats were identified. Samples of leaves and stems of 52 species were analyzed using usual techniques in plant anatomy. The reconstruction of ancestral states of characters was made in parsimony analysis using the phylogeny established for Lychnophorinae. The analyses indicated two distinct types of stems and a wide variation in foliar features, with the possible occurrence of three synapomorphies for the stems and 11 for the leaves. Adaptive pressures of restricted environments, where most species live, probably directed the evolution of morphological and anatomical diversity in Lychnophorinae.