Micromorphological Characters and Generic Delimitation of Some New World Senecioneae (Asteraceae)

Abstract

Some recent systematic investigations have placed great reliance on micromorphological floral features in generic delimitation in the Senecioneae. In order to test the taxonomic value of those features, 31 species of New World “Cacalioid” and “Senecionoid” Senecioneae were examined for five micromorphological characters: 1) configuration and distribution of the stigmatic area on the style branches, 2) stylopodial structure, 3) cellular structure of the carpopodium, 4) configuration of the anther collar, and 5) form of the endothecial cells in the anther. LM or SEM photographs were made for each character for each species. Variation was found to exist with age and geographical range for each of these characters and sometimes between florets on one capitulum. Differences in these five microcharacters were found between the “Cacalioid” and “Senecionoid” genera, but they were no more consistent than the differences in traditional characters employed in generic delimitation.