OATMAN, Kim/A.*; GAVIGLIO, Amy/M.; STEYERMARK, Anthony/C.; University of St. Thomas; University of St. Thomas; University of St. Thomas: Mitochondrial correlates of among – individual variation in maintenance metabolism

Among � individual variation in phenotypic traits is a requirement for natural selection to take place. In spite of the importance Darwin and his colleagues placed on it, this variation was seen as �noise� in the study of central tendencies until about 15 years ago. Since then, many studies have documented substantial variation in many physiological, behavioral, and morphological traits. Asking how much variation exists is only the first question. Two other fundamental questions are: does the variation have a fitness effect?; and, what are the mechanistic causes of the variation? Specifically, the last question has received very little attention, even though it addresses basic genetic, developmental, and physiological issues. In this study, we first determined maintenance metabolic rates of mice and frogs. Then, we examined several potential correlates of variation in metabolism (body mass, liver mass, cytochrome oxidase, uncoupling protein, and mitochondrial amount) in order to understand the mechanistic basis of variation in energetic traits. Neither body mass nor liver mass affected metabolic rate, but mitochondrial correlates did in both mouse and frog. Coupled with studies on the amount of variation in metabolic rate, and the potential fitness consequences of this variation, these data aid in understanding the evolutionary basis of variation in maintenance metabolism.