Meeting Abstract
Glucocorticoids are central regulators of metabolism and the response to stress. Because of the diversity of phenotypic traits that they mediate, glucocorticoid expression could be shaped by many distinct selective pressures. Previous comparative analyses within vertebrate classes suggest that glucocorticoid levels differ according to both environment and life history. Yet fundamental questions about the relative roles of specific selective pressures in shaping glucocorticoid expression in vertebrates remain unanswered. Here we use a newly developed database to test competing hypotheses about the evolution of glucocorticoid levels across vertebrates. This large database, HormoneBase, includes all available measures of plasma glucocorticoids from free-living and un-manipulated vertebrates of both sexes (>2,500 population measures). Using phylogenetically controlled analyses, we use a model selection approach to test the relative roles of energetic buffering, accumulated costs, reproductive value, environmental variability, and stressor mismatch in shaping glucocorticoid expression across vertebrates. This analysis has the potential to elucidate how specific selective pressures may shape these important mediators of phenotype. This approach also illustrates the power and potential of using large data sets, emerging phylogenetic comparative methods, and new analytical frameworks, to test questions of broad relevance to integrative biology.
