Competitive effects of a dominant arboreal ant (Azteca instabilis) on ground foraging ant diversity and community structure in a coffee agroecosystem

Species coexistence and diversity is often limited by competitively dominant species. Lowering the competitive effect of a dominant species can create areas of coexistence in the community with other non dominant species. In the Soconusco region of Chiapas, Mexico, we investigated Azteca instabilis, an aggressive, dominant, arboreal nesting ant, to determine if it lowered the competitive advantage of the dominant ground foraging species sufficiently to change the species composition and create areas of higher ant diversity around the nesting A. instabilis. Previous work shows that the effect of A. instabilis on coffee foraging ant diversity, however, this effect has not been applied to the ground foraging ant community. We conducted this study within two shaded coffee farms in the Soconusco region of Chiapas, Mexico. In a series of field sites ranging from 20x20m to 48x48m we used tuna baits at every 2 or 4 meters to determine species composition and spatial structure of the site around both grouped and isolated A. instabilis nests. Preliminary results suggest that the presence of A. instabilisincreases the diversity of ground foragers in the areas surrounding the A. instabilis nests, implying that the competitive advantage of those dominant ground foraging ant species may be reduced in the presence of A. instabilis. However, the effect appears less strongly in areas of less shade and fewer nests. These results provide further evidence that A. instabilis plays a pivotal role in shaping ant community structure and diversity.