This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2024, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment, and Phenotypes. The fellowship supports research and training of the fellow that will contribute to the area of Rules of Life in innovative ways. One of the most surprising facts about lungs is that they first evolved in fish hundreds of millions of years ago. The origin of lungs was crucial to the evolutionary success of vertebrates—lungs enabled fish to later venture onto land and diversify and enabled active buoyancy control in fishes. Fundamental questions remain about how fish regulate their buoyancy and how these mechanisms evolved. The fellow will study the anatomy, physiology, and behaviors used for buoyancy regulation across a broad range of fish species and model the evolutionary history of these traits. This research will reveal fundamental information about how fishes maintain homeostasis and interact with their environment, as well as reveal how changes in ecology and anatomy drive evolutionary changes in behavior and physiology. The fellow will develop educational STEM workshops for underserved high school students in Washington, DC, and mentor undergraduate students in the development of independent research projects related to the proposed work. The original mechanism of buoyancy regulation was the use of air breaths to modify lung or gas bladder volume. While some extant