WHEN TO LOSE YOUR HEAD: ANT-PHORID FLY INTERACTIONS, COMMUNITY LEVEL IMPACTS AND EVOLUTIONARY SIGNIFICANCE

At present, what factors generate community structure are poorly understood. In this dissertation I investigate how top-down pressure from specialist phorid-fly parasitoids, and bottom-up competition for food resources interact to determine the structure of an assemblage of omnivorous, leaf-litter ants. Chapter 2 investigates the role of interaction modifications in determining the outcome of interspecific competitive interactions for food resources. Chapter 3 explores how resource size variation and variation in the presence of phorid fly parasitoids affects the dominance hierarchy of this ant assemblage. Chapter 4 examines a trade-off between species’ abilities to dominate and to discover food resources, and how the phorid induced reduction of dominance suffered by host species changes this relationship. The final chapter proposes an explanation of the forces shaping the evolution of defense behaviors in ant-phorid interactions.