This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2025. The fellowship supports research and training of the fellow that will contribute to biology in innovative ways. Many herbivores are locked in co-evolutionary arms races with plants that produce anti-herbivory chemical defenses. Microbes living in the herbivore gut (i.e., the gut microbiome) constitute an important counter-defense, as they can produce enzymes to neutralize plant toxins. However, the mechanisms by which these counter-defenses arise remain severely understudied. When faced with potent toxins, how does the microbiome respond? Does it shift to promote microbial species with pre-existing tolerances, or do the microbes actually adapt? And do these microbiome changes primarily benefit the herbivore or the microbes? To explore these questions, the fellow will compare gut microbiome function, diversity, composition, and adaptation in Madagascar’s bamboo lemurs, which naturally vary in their exposure to dietary cyanide and offer a unique system in which to address these broad questions. The fellow will receive training in evolutionary analyses and experimentation with live bacteria. The project will be used to engage students in the U.S. and Madagascar in independent research. It will also provide valuable new insight into the biology of primate species threatened with extinction. This project will improve our understanding of how plant chemical warfare affects the herbivore gut microb