Evolutionary Studies in the Ericaceae. II. Leaf Anatomy as a Phylogenetic Index in the Andromedeae

Abstract

Leaves of North American species of Andromedeae, and certain Asian and South American relatives, were investigated anatomically. A record was made (table 1) of 26 characteristics in 20 species of Andromeda, Cassandra, Epigaea, Leucothoe, Lyonia, Orphanidesia, Oxydendrum, Pieris, and Zenobia. Primary and secondary venation, tissue distribution, and epidermal features were studied. In spite of ecological variability, every species can be identified from leaf anatomy. An index of leaf similarity shows that phylogenetic relations may exist between the following taxa: Epigaea and Orphanidesia; Zenobia and Lyonia; Lyonia lucida and either Leucothoe axillaris or the genus Pieris. The genus Leucothoe is heterogeneous; leaf morphology parallels geographic distribution of the sections. Andromeda glaucophylla has the most specialized, Pieris floribunda the most generalized, leaf morphology of the several species studied. Caution should be used in interpreting leaf characteristics as habitat responses; there is considerable genetic fixation. Cassandra and Andromeda, both bog plants, have entirely different vein patterns.