The derivation, utility and implications of a divergence index for the fynbos genus Leucadendron (Proteaceae)

Abstract

The genus Leucadendron is useful for a phylogenetic study because it contains many species (79), is morphologically very diverse and appears to have diverged early on in the history of the family in Africa. Polarity of many characters was determined by outgroup analysis and the ontogenetic method. Exceptionally high levels of convergence made the determination of the phylogeny of the subsections problematic. An index, which is the sum of weight of all derived characters present in a species, was determined. The genus should be removed from subfamily Aulacinae and placed closer to the Leucospermum‘alliance’. I suggest an arid temperate, shrub-like origin for the African Proteaceae, which is in contrast to some published viewS. Modifications to accepted concepts of fruit homology and evolutionary trends such as pollination and dispersal are presented for the family. The divergence index, if used as a ‘morphological clock’, appears to be useful for further biogeographic and ecological analyses.