Influence of an invasive ant on grazing and detrital communities and nutrient fluxes in a tropical forest

Aim  Pathways linking grazing and detrital subsystems of terrestrial ecosystems are important for ecosystem processes and function, but remain poorly understood. The invasion of a generalist predator creates a unique opportunity to study the effects of predation across these subsystems. We examine here, the effects of a non-native generalist predator, the little red fire ant ( Wasmannia auropunctata, Roger) on both grazing and detrital invertebrate communities and ecosystem processes in a rain forest understorey.
Location  Gamba Protected Area Complex, south-western Gabon, Africa.
Methods  We measured abundances and diversities of understorey grazing and detrital invertebrate communities, soil nutrients, herbivory, litter fragmentation rates and leaf chemistry of a dominant understorey shrub inside and outside of 19 separate invasion fronts. We then explored possible trophic cascades and pathways of interaction using path analysis.
Results  Results suggest that invasive ants may alter herbivory regimes, grazing and detrital communities, and may indirectly alter litter decomposition and nutrient cycling in the soil by suppressing important microbivore and detritivore populations with consequences for leaf chemistry.
Main conclusions  These results demonstrate that generalist predators may be major drivers of both grazing and detrital subsystems by inducing strong shifts in adjacent communities that ultimately affect ecosystem processes.