One of the most important events in vertebrate evolution was the evolution of endothermy (i.e., the physiological ability of animals to raise their body temperature above the ambient environmental temperature). The aerobic capacity model attempts to explain the evolution of endothermy by hypothesizing that endothermy evolved as a correlated response to natural selection on aerobic capacity (maximal oxygen consumption during exercise). A key assumption of the model is that resting metabolism and aerobic capacity are positively correlated because they are inescapably, mechanistically linked. To date no study has falsified this assumption, so the model stands as a viable explanation for the evolution of endothermy. The proposed studies will use artificial selection (breeding experiments) to test the key assumption of the aerobic capacity model. Two types of artificial selection will be used. The first will be artificial selection on aerobic capacity. This selection will produce lines of mice with low aerobic capacity and lines of mice with high aerobic capacity. If selection for increased aerobic capacity produces no response or a decrease in resting metabolism, the aerobic capacity model will be falsified. The second type of artificial selection is designed to directly and experimentally test the model's key assumption (i.e., that a positive correlation between resting metabolism and aerobic metabolism is a fundamental design constraint that characterizes the physiology of terrestrial vertebrates). Artificial selection will be used in an attempt to generate lines of mice for which there is a negative correlation between resting metabolism and aerobic capacity. If a negative correlation can be produced, then the aerobic capacity model will be falsified. The biochemistry, anatomy, and physiology of all the selected lines of mice will be studied to help elucidate the mechanistic basis for aerobic capacity. These studies should be of interest to ecological and evolutionary physiologists, exercise physiologists, and evolutionary biologists.
Broader impacts of the studies will be three-fold. First, the experiments will develop genetic resources (lines of mice) that can be used as models for studying the genetic and mechanistic bases of aerobic capacity. Second, diverse training will be provided to one or more postdoctoral researchers, graduate students, and undergraduates. Third, building on an existing program that the PI helped develop, the PI will attempt to recruit local high school science teachers and students to participate in the research and to pursue related studies.
