Influence of genetic variation on colony-level foraging behavior of the red imported fire ant (Solenopsis invicta)

Among social insects, genetic variation in a behavior can allow a colony to exhibit more flexible, rapid responses to environmental changes and promote homeostasis. Such variation enables adaptive evolution and can increase colony fitness in multi-lineage colonies, such as polygynous fire ants. Our preliminary research demonstrated significant and persistent colony-level variation in fire ant foraging behavior. Here, we examined potential causes and consequences of this variation. To examine potential genetic influences on colony-level variation in foraging behavior, we founded single-lineage colonies and assayed foraging behavior in standardized experimental colonies. Colonies varied significantly in foraging related behaviors, and upwards of 70% of this variation could be explained by worker genetic lineage. Variation in foraging behaviors has been associated with variation in expression of the foraging gene (for) in a wide variety of organisms. We examined the effects of cGMP-dependent protein kinase G (PKG), the enzyme product of for, on foraging behavior by treating lab colonies with 8-Br-cGMP to artificially activate PKG. Behavioral assays revealed that this treatment had a significant effect on fire ant recruitment and predation compared to control colonies. Notably, changes in fire ant foraging behavior had significant indirect effects on plant damage due to herbivory. Currently we are assaying field and lab colonies for variation in for gene expression. This study suggests that significant variation in foraging behavior exists among fire ant colonies and may underlie variation in the ecological effects of fire ants and variation in methods necessary for their control.