Effect of an exotic Acacia (Fabaceae) on ant assemblages in South African fynbos

Abstract

Ant assemblages in South African fynbos invaded by Acacia saligna were compared with ant assemblages in undisturbed fynbos to determine whether ant assemblages change under exotic plants that produce ant-dispersed seeds. Overall, no differences in the species richness of ants were found between weed-infested and native sites but there were differences in both ant abundance and the composition of the ant assemblage. Ants were much less abundant in weed-infested sites. To investigate whether changes in ant assemblages in weed-infested areas could be due to a preference for native seeds over exotic seeds, seeds of a range of species were offered to ants and ants that handled seeds were identified. Thirteen species of ants handled A. saligna seeds and there was no evidence to suggest that the ant assemblage as a whole preferred native seeds to A. saligna seeds. Hypotheses that may account for this pattern are discussed.