Mediation of optimal reproductive decisions by maternal stress

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Population and ecosystem health are driven by the capacity of individuals to maximize their fitness under continuously changing environmental conditions. Since physiological function directly mediates the relationship of the organism to its environment, physiological traits are useful to study as regulators of the life-history decisions and trade-offs that shape variation in fitness. However, despite much theoretical work predicting expected relationships between physiology and ecological or environmental processes, many physiological traits fail to show consistent individual-level variation, cannot be universally applied across diverse taxa, or are hard to experimentally manipulate in wild systems. Steroid hormones are now recognized to be critically involved in the adaptation and evolution of complex traits. Baseline levels of ‘stress’ hormones are fantastic candidates for mediating investment decisions both within and among individuals since they regulate daily and seasonal energetic balance in vertebrates. Although recent work has focused on trying to link stress hormones directly to fitness, these studies often find equivocal results. Very few studies are designed to interpret more complex, but likely more biologically relevant, linkages between baseline stress hormones and fitness. The research program and associated projects outlined in this application are designed to answer some of these fundamental, and yet currently missing, questions. I am specifically going to test whether baseline stress hormones: i) integrate individual and environmental variability, ii) prepare individuals for the performance demands of energetically expensive life-history stages, iii) mediate adaptive investment decisions, and therefore fitness, and iv) modulate their trade-off and fitness effects via ecological and life-history level contexts. This type of mechanistic information is not only very important for basic exploratory scientific studies, but it is increasingly key and needed in applied research to increase the predictive power of how we expect individuals and populations breeding in sensitive ecosystems like the Arctic to fair and respond as they face increasingly numbers of human-induced stressors.