Evolutionary Physiology of Drosophila melanogaster

Over the past 30 years of experimental evolutionary research on Drosophila, strong functional associations have been established between organismal characters, life history, and behavior. Evolutionary physiologists use stress as a tool, either to measure an organism’s physical robustness, or to create differentiated populations with which to study adaptation. However, many questions are unanswered. For example, do short periods of strong selection generate similar levels of functional divergence to those generated by long-sustained selection? And if so, can we take the already advantageous Drosophila model system and use it to effectively study vertebrate diseases (i.e. cardiovascular disease and obesity-related disorders). Chapter 1 examines the relationship between evolutionary history and physiological differentiation. We observed classic physiological characters, specifically stress resistance and locomotion, as well as a character of recent interest, heart robustness. We found that short periods of strong selection applied to outbred Mendelian populations can readily generate high levels of functional differentiation. Chapter 2 revolves around the interrelationships among major physiological systems. By combining electrical pacing and flight exhaustion assays with manipulative conditioning, we started to unpack the interrelationships between cardiac function, flight endurance, and stress resistance. One major insight is the adverse impact of lipids on Drosophila heart robustness, a parallel result to many comparable studies in human cardiology. With human obesity growing to epidemic proportions in the United States, and excessive lipid accumulation being a risk factor for heart disease, we sought to observe the effects of lipid accumulation in Drosophila. Chapter 3 discusses the effects of intense selection for increased starvation resistance on ten outbred Drosophila populations. These populations displayed cardiac dysfunction, increased adult mortality, and elevated lipid levels, making them a useful model system for heart disease and obesity-related disorders. In Chapter 4, I emulated the effects of chronic consumption of the high-fat, high-caffeine fast-food diet by exposing flies to coconut oil and caffeine. Similarly, the findings here continue to support the general inference that high lipid levels present challenges for the Drosophila heart. Fruit flies could be an invaluable resource in understanding the molecular, genetic and other machinery underlying heart disease