The assembly of a temperate coniferous forest ant community

My dissertation addresses the question of whether communities of species are structured in predictable or random assemblages. The thesis comprises an analysis of both abiotic and biotic factors affecting community structure within and among open space reserves. Ants play key roles in terrestrial invertebrate communities and are an important model system in studies of community assembly rules. I used ants to test whether stochastic or deterministic factors affect the structure of communities.;This study focused on ant communities in the foothills of the Colorado Front Range. These ant communities occupy an ecotone between grasslands and coniferous forests. The unique characteristics of this habitat allowed me to examine the interaction between the ant species and their habitat. I experimentally manipulated nest sites to evaluate the effects of nest-site availability and distribution on community structure. I removed rocks at five different locations and replaced them with flagstone tiles. I found that nest sites are important for the structure of ant communities. Ants occupied more than 70% of available nest sites in the spring when colony growth was high. Soon thereafter, ants abandoned nest sites. The distribution of nest sites also affected local distributions of species. Species richness was greatest when nest sites were aggregated. My work sheds new light on mechanisms driving species distributions at local scales.;I also assessed the competitive interactions among species to determine their effect on community assembly. I used tuna and sugar baits to examine dominance-discovery relationships among ant species. I found that the temperature that ants are active decreases the frequency of interspecific interactions. At most locations, discovery was more important than dominance. Once a worker ant discovered baits, it recruited other workers and excluded access by other species. The most common species found nesting under tiles were also dominant at baits, suggesting they might have a competitive edge over those that do not recruit workers.;Both stochastic and deterministic factors affect the structure of ant communities. At a regional scale, ant communities appear to be structured by competition, however local communities are random assemblages of the regional species pool.