The taxonomic utility of micromorphology in Lepidaploa (Vernonieae: Asteraceae)

Abstract

Lepidaploa belongs to the Vernonieae tribe, one of the most complex tribes of Asteraceae. Nowadays, the relationship between Lepidaploa and its related genera is poorly understood. Different microcharacters might be of great taxonomic value and may be used in the identification of different taxonomic categories. The morphology of the microcharacters of phyllaries, florets and cypselae was analysed in detail for the first time in species of Lepidaploa to evaluate their reliability as taxonomic markers. The results were also discussed in relation to other closely related genera of the Vernonieae tribe. Microcharacters of 23 species were studied using stereo, light, and scanning electron microscopy. Lepidaploa displays high variety of microcharacters, such as trichome types and crystals. Eight trichome types (non?glandular and glandular trichomes) were observed on phyllaries, florets and cypselae. The combination of these trichome types on the different structures, as well as crystals, basal stylar node and idioblasts are taxonomically important to differentiate related species. Glandular apical appendage was observed only in L. pseudomuricata. This study demonstrates that the combination of floral microcharacters is valuable within genera to differentiate related species. However, they are of little utility to distinguish closely related genera.