Understanding constraints and potentials of weed management through seed predation by harvester ants

The variability of seed predation in time and space may provide opportunities to weeds to escape predation. Seed predation rates by harvester ants in dryland cereals were among the highest ever recorded on arable fields (46-100%). The timing of weed seed shed overlapped with the period of highest demand. The spatial nest arrangement appeared to be non-random. The large nests were more or less regularly distributed, small nests tended to be more clumped. Harvester ants responded with extremely high predation rates (99-100 %) to all densities of Lolium multiflorum L. seeds applied (1000-20000 seeds m-2), and the response was density independent. Patch size influenced predation rates by harvester ants. Estimated seed predation rate was highest in the largest patches (99-100%), and lowest in the smallest patches (78-94 %). The current research quantified temporal and spatial variability in seed predation in dryland cereals and the influence to the efficacy of granivory.