Role of Nature and Nurture for Caste Determination in Pogonomyrmex barbatus

Indianapolis, IN

Nature and nurture can each have their own effect on the phenotype of an organism and the two can interact whereby the environment can change how the genes interact with each other. For example, in honey bees, genetically identical honey bees could have different phenotypes, queen or worker bee, based on the diet they received. Our hypothesis is that nurture plays a role in caste determination of harvester ants. Like honey bees, ants are eusocial insects. However, unlike honey bees, Pogonomyrmex barbatus harvester ants have genetic caste determination. In this dependent lineage system of caste determination, workers are produced as a result of inter lineage mating while queens are produced as a result of intra lineage mating. Even with a strong genetic component, the phenotypic plasticity of caste determination is not completely lost, as evidenced by rare inter-lineage queens and intra-lineage workers. Furthermore, queens and workers also have different ratios of nitrogen and carbon in their body, and assimilate qualitatively different diets. These observations suggest that there is nature and nurture interaction present, making harvester ants an ideal organism to examine the relationship between genetic and environmental interactions. We grew colonies of P. barbatus (J-lineage) on different diet treatments, with different protein to carbohydrate ratios. Treatments have been maintained for several generations of cohort production (~6 months) and here we report how available nutrients affect both colony growth (optimal diets) and caste determination.