Effects of Seed Predation by Ants on Seedling Densities at a Woodland Site in SE Australia

Abstract

Ants are by far the most important post-dispersal seed predators at a woodland site in SE Australia, and they rapidly remove many seeds from the ground. This paper uses experimental manipulations of seed densities and ant populations to examine the likely impact of seed predation by ants on seedling recruitment in Eucalpytus baxteri and Casuarina pusilla. When seedfall was light, as usually occurs in the absence of fire, the elimination of ants resulted in a 15-fold increase in seedling densities for E. baxteri, whose seeds are removed at particularly high rates. Seeds of C. pusilla are removed less rapidly by ants, and increases in seedling densities following ant elimination were less marked for this species. Experimental dumpings of seeds at high densities, simulating the massive release of seeds from woody fruits which occurs following fibre, resulted in predator satiation and in comparison to controls produced high numbers of seedlings. These results suggest that seed predation by ants limits seedling recruitment in the absence of fire, and that predator satiation plays an important role in successful recruitment following fire.