NEST SITE DENSITY OF LEAF CUTTER ANTS (ATTA CEPHALOTES) ACROSS LAND-USE TYPES IN COSTA RICAN LOWLAND RAIN FOREST
Deo Lachman, Jane Zelikova.
University of Wyoming, Laramie, WY.
Leaf cutter ants are the most dominant herbivore in the Neotropics and are ecosystem engineers that alter soil chemistry and composition around their nests. While many studies have investigated the intricacies of their fungi-ant mutualism and the resulting biogeochemical effects, few attempt to make these findings scalable in a meaningful way. We conducted our study at La Selva Biological Research Station in Costa Rica. La Selva is home to a variety of habitats including primary old growth forest, secondary forest, regenerating pastures, and both active and abandoned plantations. We were interested in finding out how nest densities and nest size varied across these different habitat types. We hypothesized that nest densities would be larger in regenerated open pastures, and that nest size would be smaller in areas of higher density. We comprehensively surveyed 65 5,000 m² plots across habitats throughout La Selva. We marked each nest and measured nest surface area, counting nest entrances and vents. We found that nest densities in regenerating pastures were significantly higher than densities for all other habitats. However, a calculation of habitat area covered by nests did not show a statistically significant difference across habitats. This means that areas of higher density do tend to have smaller nests than those found in areas of lower density. These results support the hypotheses that nest size and density vary across habitats. Furthermore, they can be used to quantify the impact of ecosystem engineers at large scales and across other tropical forests.