Modes of dispersal of seeds in the Cape fynbos

Abstract

An analysis of phytosociological data from the various shrubland communities in the Mediterranean climate zone of South Africa, based on the contribution of species to total canopy cover, showed differences between community-wide modes of dispersal in different vegetation formations. In undisturbed Renosterveld, 39% of important species are dispersed by animals, 23% by wind and 34% passively. Once Renosterveld is disturbed, wind-dispersed species increase to 32% at the expense of animal- and passively-dispersed plants. In Standveld, animal-dispersed plants are most important (44%), followed by wind (31%) and passively-dispersed plants (19%). On the arid fringes, however, plants dispersed by animals, especially birds, decrease and passively-dispersed succulents increase. In the Succulent Karoo, 52% of common species are passively-dispersed and 33% are wind-dispersed, with animal-dispersed species comprising only 7%. The heathlands of the Cape are very difficult to analyse because of the high degree of diversity and turnover rates, thus local dominance patterns are greatly influenced by disturbance history. It is suggested, however, that passively-dispersed plants comprise some 50% or more in the heathlands, and those dispersed by animals (mainly ants) may locally comprise up to 30% of dominants. Forest species on the other hand are essentially bird-dispersed.