Ant populations and their distribution are affected by many circumstances. Abiotic factors such as weather, water availability, and soil characteristics may determine if a habitat is suitable for ants. Other factors such as level of disturbance, available food resources, reproductive biology, and natural enemies also contribute to defining ant distribution. Three ant species in East Baton Rouge parish, Louisiana were studied to determine what factors affected their distribution by measuring abiotic and biotic factors at sampling sites throughout the parish. These factors included weather, water availability, vegetation types, level of disturbance, and soil characteristics. Factors which predict abundance of Solenopsis invicta (RIFA), Linepithema humile (Argentine ants), and Brachymyrmex sp. (rover ants) were analyzed with stepwise regression, backward regression, and r-square selection method. The number of red imported fire ants foraging at Vienna sausage vials and honey vials were affected by cloud cover, vegetation type, relative humidity, and distance to nearest water source. Mounds of RIFA were most affected by percent of clay in the soil. Abundance of Brachymyrmex was affected by vegetation type, canopy cover, and bulk density, and presence of Argentine ants was affected by temperature, relative humidity, and bulk density. Bulk density may be associated with areas of high disturbance which would lead to soil compaction.
Another study was conducted in the laboratory to determine the level of aggression demonstrated by RIFA and Argentine ants when they were allowed to interact. Intraspecific nestmate and non-nestmate interactions were observed for both RIFA and Argentine ants. Interactions between lab-reared RIFA and field-collected RIFA were also examined. The level of aggression, role of the ant (initiator or respondent), and mortalities were studied. Chi-square, logistic regression, and mixed model analyses were used to determine significant effects. When RIFA and Argentine ants interact, Argentine ants face a higher risk of mortality even though Argentines were the initiators. Lab-reared fire ants were less aggressive toward each other than toward field-collected RIFA and Argentine ants. These aggression bioassays will help determine what occurs in the field at the interface of the two competing species and how this may affect their distribution.