Some Consequences of Diffuse Competition in a Desert Ant Community

Abstract

Exploitative and interference competition are investigated in detail in a community of 6 coexisting species of granivorous desert ants [Novomessor cockerelli, Pogonomyrmex rugosus, P. desertorum, Pheidole desertorum, P. xerophila and P. sitarches]. A linear model that includes both direct and indirect competitive interactions is used to predict positive or negative correlations in the abundances of competitors. Data on the abundances of the 6 ant species on 23 1/4 ha plots provide empirical support for the 4 predictions so generated. Apparent facilitation, in the form of positive interspecific spatial associations of colonies, is detected between 2 competitors and interpreted as arising from indirect pathways of interspecific interaction. How indirect interactions among species at a single trophic level may play a significant role in organizing natural communities are illustrated.