THE DISTRIBUTION OF MISTLETOES IN SOUTH-AFRICA - PATTERNS OF SPECIES RICHNESS AND HOST CHOICE

We analysed distribution records of mistletoes (Loranthaceae and Viscaceae) in South Africa in terms of host taxa and geographic patterns. Few species are found in nutrient-poor Cape shrublands (fynbos) and in the southern evergreen forests on nutrient-poor sands. The most species-rich areas are the nutrient-rich mesic savannas (including Valley Bushveld, a subset of savanna). Mistletoe species richness is significantly correlated with the average nitrogen levels of the woody plants in any biome, suggesting that the overall nutrient status of a biome influences mistletoe species richness. The analysis of host-choice of mistletoes also indicates a non-random distribution; thirty-three genera in twenty-two plant families host from three to twenty-four different mistletoe species, suggesting that parasitism is not related to phylogenetic position. The most important host genera are Acacia (hosting twenty-four spp. mistletoes), followed by Combretum (fourteen), Maytenus (thirteen) and Rhus (twelve). The species richness of mistletoes on host genera is significantly correlated with mean host N, and in four of five areas sampled, the number of mistletoes on host trees was significantly correlated with host N.