Subclass:
Asteridae
Links to Family Pages:
Subclass consisting of 49 families, and nearly 60,000 species of angiosperms - one of the largest subclass in terms of number of species. The Asteridae encompasses most of the Englerian group referred to as the "Sympetalae" that possesses a corolla tube. The vast majority of the Asteridae have sympetalous flowers, in which the stamens are isomerous and alternate with the corolla lobes, or fewer than the corolla-lobes, and ovules with a single integument layer. The subclass is the most specialized group of dicots, and more than any other subclass exploits specialized pollinators and specialized means of presenting pollen. Chemically the Asteridae are noted for the frequent occurrence of iridoid compounds.
The Asteridae make a relatively late entrance into the fossil record. Molecular phylogenetic studies indicate that the Asteridae are a natural group only if other sympetalous orders from the Dilleniidae and Rosidae (e.g., Ebenales, Ericales, and Primulales) and the Cornales and Apiales are included in an expanded Asteridae. The Asteridae are sister to or derived from within the Rosidae.
