Correlational selection on physiology and alternative male strategies

Both reproduction and whole-organism performance are influenced by the endocrine system, and all of these traits have heritable, genetic components. Elucidating links among genetics, reproductive function, performance, and the endocrine and immune systems is essential to understanding how evolution has shaped reproductive strategies and physiology. Systems with discrete polymorphisms provide good models for examining the relationships among these traits since variation both within and among morphs can be examined. Male side-blotched lizards (Uta stansburiana) have three different color morphs (orange, blue, or yellow throat), which arise from a gene of major effect. Each of the types exhibits a different physiological and mating strategy (defense of a large territory with multiple females, defense of an individual female, or 'sneaking' into another male's territory). In particular, territorial orange-throated males have high stamina and high levels of plasma testosterone, relative to the other two types. However, these males also have higher mortality rates than the other morphs. Testosterone may decrease the capability of the immune system to cope with infectious agents. In laboratory breeding studies, sprint speed, endurance, and standard metabolic rate of parents and progeny with known throat color genotypes will be measured. In the field, variation in plasma hormones (testosterone and corticosterone) and their effects on sprint speed, endurance, and field metabolic rate will be studied. DNA paternity analysis will provide field pedigrees to complement genetic studies in the laboratory. These experiments will allow the investigators to evaluate the links among hormones, physiology, and reproduction. Currently no data are available to address relations between genetics, physiology, performance, and reproduction; this research accomplishes this major goal and establishes a database for future work. Our work addresses the fundamental forces that shape the joint evolution of endocrine function, physiology and immune function.