Morphology and taxonomic significance of the leaf epicuticular waxes in the Epacridaceae

Abstract

The leaf epicuticular waxes of all genera within the Epacridaceae have been studied. Amorphous wax and three structured wax types, namely plate, ribbon and tube wax are described and their occurrence within genera surveyed. The distribution and development of waxes on the leaf lamina surfaces and on petioles is outlined and the consistency of wax-types within species examined. Additional features such as the presence of papillae and trichomes, the distribution of stomata, and the distribution and prominence of cuticular outgrowths have been observed, extending earlier studies of these features. Amorphous wax and plate wax are widespread within the family, while tube wax is found only in two genera (Dracophyllum and Richea) and ribbon wax is restricted to genera within the tribe Styphelieae. An evolutionary pathway from ancestral amorphous wax to plate wax, with later independent development of tube wax and ribbon wax is suggested. The taxonomic value of the wax data is discussed in relation to current generic delimitation and supra-generic classification and to recently proposed changes.