Variation in Predispersal Seed Predation in Several Australian Acacia spp.

Predispersal seed predation was examined in seven Acacia spp. over both time and space. Each species was associated with a particular major seed predator. Two species, A. elongata and A. myrtifolia, each had a host-specific seed predator: Melanterius acaciae (Coleoptera: Curculionidae) on A. elongata and Diethusa sp. (Coleoptera: Curculionidae) on A. myrtifolia. Three other species were preyed on by Melanterius corosus, whilst the remaining two species were preyed on by M. maculatus. Variation in the degree of predispersal seed predation was apparent both between populations of any particular Acacia sp. and within species over consecutive fruiting seasons. Some of this variation is in response to varying seed-crop sizes and associated predator satiation. However, since the dynamics of the weevil populations are unknown, much of the variation remains unexplained. Where Acacia spp. occupied the same habitat and were both attacked by one species of predispersal seed predator, differences in seed predator attack were apparent. A. linifolia was more susceptible to M. maculatus attack than was A. terminalis, and A. suaveolens was more readily attacked by M. corosus than was A. longifolia. No differences in seed predator attack were found between A. suaveolens and A. ulicifolia. The importance of this seed predation on the dynamics of the host species is briefly discussed.