Dominant meat ants affect only their specialist predator in an epigaeic arthropod community

Abstract

Ants are thought to exert an important influence on the structure of arthropod assemblages through predation and competition. I examined the effect of a dominant ant, Iridomyrmex purpureus, on epigaeic arthropod assemblages on rock outcrops using an exclusion experiment. I compared arthropod assemblages on four replicate outcrops allocated to each of the following treatments: I. purpureus present; I. purpureus absent; I. purpureus excluded; and procedural control. Nests of I. purpureus were caged in summer 2001 and epigaeic arthropod assemblages were sampled at all sites using pitfall traps in autumn and spring 2001 and summer 2002. I also collected items from foraging workers to determine the diet of I. purpureus. Exclusion cages successfully reduced the abundance of I. purpureus workers in pitfall traps by more than 97%. Exclusion of I. purpureus did not affect the size distribution, biomass or abundance of arthropod predators or non-predatory arthropods, although the total biomass of ants was greater at sites with I. purpureus. Spider biomass, species richness, abundance and composition were also not affected by the presence of I. purpureus, although the I. purpureus mimic and specialist predator, Habronestes bradleyi, became less abundant at sites from which I. purpureus was excluded. Predation by I. purpureus on other arthropods may not have a significant effect on epigaeic arthropod communities, but the complex role of I. purpureus in this ecosystem and the high diversity of species belonging to multiple trophic levels may obscure its effects in this system.

Effect of canopy openness on the pressure of predatory arthropods and birds on epigeic insects

“…This is in accordance with most studies focused on methodology of predation rate measurement [25,26,32]. Predation rate has predominantly been measured indirectly through predation exclosure techniques [26,[33][34][35][36], which provide sufficient estimates of absolute predation risk. Although direct predation measurement has been employed only in a minority of studies [3,4,37,38], it is considered a better alternative for comparing different habitats, identifying predators, and estimating time of attack [3,26].…”

Ants in citrus: impact on the abundance, species richness, diversity and community structure of predators and parasitoids

“…Whereas several studies have demonstrated a negative impact of ants on the abundance of natural enemies (Eubanks, 2001;James et al, 1999;Kaplan and Eubanks, 2005;Piñol et al, 2012a) others find no effect (Chong et al, 2010;Gibb, 2003;Offenberg et al, 2005) or even find positive effects of ants on the community of natural enemies (Peng and Christian, 2013;Stewart-Jones et al, 2007). The same or even greater variability is reported at the species level; natural enemies, even species belonging to the same taxonomic order, may be affected differently by ants.…”

Impacts of major predators on tropical agroforest arthropods: comparisons within and across taxa

“…However, for most intermediate sampling periods, ants did not affect total arthropods, but did influence particular orders. Gibb (2003) removed Iridomyrmex purpureus and found no effects on groundforaging arthropod assemblages. Furthermore, Koptur (1984) found that different ants varied in their abilities to remove caterpillars from Ingatrees.…”

“…Thus although ants may protect Inga spp. from herbivores, effects on ant-plant arthropod assemblages are largely unknown (see Risch and Carroll 1982;James et al 1999;Gibb 2003).…”