9509312 Cole Throughout western North America the harvester ant, Pogonomyrmex occidentalis, is one of the dominant animal species; it is an important component of the desert landscape. The goal of the current research is to determine how the density and distribution of these organisms are regulated. Two possible mechanisms influence population density: the availability of recruits and the availability of food and space for the colonies. These two need not be mutually exclusive. Both the availability of food and space and the numbers of recruits will be experimentally modified to measure the effect on population density. The experimental studies on the regulation of population density and colony distribution will be combined with measurement of temporal and spatial variation in the patterns of recruitment to extend the understanding of local processes to large geographical scales. Pogonomyrmex occidentalis is the primary disperser of seeds in a fragile ecosystem subject to multiple uses. By determining the factors that govern the population size and distribution in this important species, this research may elucidate the mechanisms that govern range quality and habitat preservation.
