The interactive effects of climate, life history, and interspecific neighbours on mortality in a population of seed harvester ants

1. Fifteen years of census data from a population of the red harvester ant (Pogonomyrmex barbatus), 5 years of census data from populations of Aphaenogaster cockerelli and Myrmecocystus mimicus at the same site, and longterm precipitation data from a nearby weather station were used to examine how nearest interspecific neighbours, climate, and life history influence P. barbatus colony mortality. 2. It was found that more P. barbatus colonies die following dry summers than following wet summers, but there is no relationship between the establishment of new colonies and rainfall. 3. Aphaenogaster cockerelli, but not M.mimicus, nearest neighbours influence P. barbatus colony mortality in some years and for some ages. 4. The effects of nearest A. cockerelli neighbours are usually most severe following dry summers, when resource availability is reduced.