Numerical classification of Rhododendron (Ericaceae) based on seed morphology and protein profile

Abstract

Seeds of 28 taxa and infra-specific taxa of Rhododendron were examined by light and electron microscopy and their protein patterns were determined by SDS-PAGE analysis. A combined data matrix was subjected to numerical analysis by Sørensen’s similarity measure and Ward’s clustering method to generate a dendrogram expressing the hierarchical phenetic relationships between the taxa. Two main groups have been recognized, of which one comprises two smaller groups, while the second is divided into three groups. Comparison between the five low-level groups and the subgenera in the two major traditional classifications of Rhododendron has shown that none of these subgenera is taxonomically secure. Infra-specific taxa of Rh. brachycarpum and Rh. minus adhered closely to each other, and the former species was isolated from the remaining taxa in one of the five low-level groups. Separation of Rh. menziesii into a genus (Menziesia) has not been supported and it seems best placed in the subgenus Hymenanthes.