Intellectual Merit. The combined challenge of low food availability and low temperatures can make winter a particularly difficult time for survival and reproduction. In order to be successful, individuals must survive and reproduce. Traditionally, behavioral biologists interested in seasonal phenomena have focused on reproductive adaptations, and have largely ignored adaptations associated with survival. Different life history strategies have evolved in different species to optimize the timing of investment in important life functions, such as growth, reproduction, or survival. The proposed research will assess immune function as a 'proxy' for survival costs in several different conditions. Life history strategies are based on the conflicting roles of survival versus reproductive functions in fitness. Reproductive activities generally compromise survival, whereas energy devoted to survival compromises generally reproductive success; however, these demands vary seasonally. Outside of the breeding season, individuals often invest more resources into mechanisms that promote survival until the next breeding opportunity. The working hypothesis of the proposed research is that photoperiod (day length) modulates the trade-offs between reproductive and survival mechanisms.
During the next five years, five specific aims will be addressed. In Aim 1, the trade-offs between immune activation and fitness will be examined in rodents by studying the effects of real or mock antigens on the number of offspring and grand-offspring produced. In Aim 2, the interaction among several environmental factors that vary across the seasons will be assessed on immune function and torpor. Aim 3 will examine the mechanisms underlying photoperiodic modulation of immune function by determining whether the pattern of clock genes expression in the spleen or other lymphatic tissues provides calendar information. Aim 4 will examine whether photoperiod mediates social avoidance of infected individuals. Aim 5 will examine how the relationship among winter stressors, immune function, and photoperiod affects morphological symmetry. Taken together, the primary intellectual merit of this proposal is the novel and important information gained about the trade-offs between immune function and reproduction from the perspective of molecular mechanisms, physiology, and behavior.
Broader Impact. The project will provide interdisciplinary research opportunities for training undergraduate, graduate, and postdoctoral trainees, including women and students from historically-underrepresented groups.
