DISSERTATION RESEARCH: The evolution of plant-ants: mutualism and the gut microbiome

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Ants are the most numerous animals in many terrestrial ecosystems. For example, they comprise more than 90% of insects in the canopy of tropical rain forests. This numerical dominance means that not all ants can be predators, as was once thought. Some species must instead feed on nutrient poor, plant-based resources. Acacia-ants are a good example. They live in acacia trees and feed exclusively on resources provided by these trees. In exchange for nesting space in the trees and food (mostly nectar), the ants aggressively protect host trees against insects that eat leaves, and against competing plants and disease-causing fungus. However, the nutritional content of the nectar provided by acacias is insufficient for the ants, raising the question of how colonies of acacia-ants obtain enough nourishment to sustain themselves. A possible clue comes from recent work with other animals, including humans, showing that bacteria living in the gut help to extract important nutrients from food. This research will determine whether acacia-ants also depend on bacterial partners for dietary enrichment, and how such partnerships have evolved.This study will help us understand how animals -- perhaps including humans, some day -- can live on nutritionally poor food. Because ants are influential and dominant members of many ecosystems, understanding how they obtain nutrition is essential for generating a comprehensive picture of energy flow through the environment. More generally, this work will teach us about the ever-increasing role of bacteria in our lives and in the natural world; the importance of bacteria in the evolution of all animals is just beginning to be appreciated. The researchers on this project will mentor students in research and will share their results through presentations to the public and through a blog about ants on the worldwide web.