Ecosystem engineers are profoundly important in many biological communities. In the neotropics, one taxonomic group considered to have engineering effects is the Formicidae (ants). Leaf-cutter ants in particular, which form extensive colonies of up to eight million individuals, can be important ecosystem engineers in tropical environments. While the effects of leaf-cutter ants on plant community structure and soil chemistry is well-studied, their effects on consumers are poorly understood. Therefore, we examined the indirect effects of the leaf-cutter ant Atta cephalotes on the leaf-litter arthropod community. We compared abundance and diversity patterns at ant nests compared to areas distant from nests, utilizing both a factorial design and a gradient analysis.
Results/Conclusions
We found that arthropod abundance and diversity was significantly lower for multiple taxonomic groups and trophic levels near leaf-cutter nests, and this pattern was strongest at night. Exceptions to this pattern included two morphospecies of Collembola that were more abundant on nests, suggesting some specialization for these species. For the gradient analysis, abundance increased exponentially for most groups of arthropods. However, for the dominant arthropod species, the amphipod Cerrorchestia hyloraina, a quadratic function was the best fit curvilinear model for abundance. It appeared that C. hyloraina had maximal abundance at the transition between nest site and less disturbed forest. These results indicate that leaf-cutter ant activity has a strong effect on the leaf-litter arthropod community, adding to spatial heterogeneity within neotropical forests. These effects may translate into changes in important ecological processes such as nutrient cycling and food web function.