Genetics and task selection in the red imported fire ant

Polygyne red imported fire ants are able to reach much higher densities than the monogyne social form.  One proposed mechanism for this is complementarity of the component genotypes of the colony. As fire ants need both sugar and protein sources for maximal colony growth, a diverse array of workers searching for a diverse array of resources would help a colony reach its optimum.  There is some evidence that fire ant families differ in their foraging behaviors, but this has yet to be shown in the context of a polygyne colony.  In order to test whether the component families of polygyne colonies specialize on specific tasks, I laid protein and carbohydrate baits around fire ant colonies in Texas to collect foragers at different resources, disturbed the mound to collect interior workers, and searched plants for workers along transects radiating from the mound.  Ants were then subjected to microsatellite analysis to determine the family identity of workers for specific tasks.  I found that task selection by workers was strongly influenced by their family identity in foragers and exterior workers, but no detectable task differentiation based on genotype existed in interior workers.  These results strongly imply that complementarity of genotypes plays a role in the polygyne social form’s ability to reach much higher densities than their monogyne counterparts.  Furthermore, these results suggest that the benefits of increased relatedness as proposed by kin selection theory could be replaced by alternate benefits when multiple genotypes exist within a single colony.