Meeting Abstract
Glucocorticoid hormones are dynamic and flexible, and allow animals to cope with perturbations in their environment by coordinating behavioural and physiological responses. As a result, glucocorticoids (CORT) often play a role in shaping fitness and are thought to promote adaptive responses to environmental change. Despite the importance of CORT as a mechanism of phenotypic plasticity, little is understood about how this coping mechanism arises as most studies on the topic have been performed at an ecological scale rather than an evolutionary one. Though breeding experiments in captive animals have demonstrated that CORT can respond to artificial selection, little is understood about if and how endocrine systems evolve in free-living systems. We use a longitudinal hormone and fitness dataset collected in North American red squirrels (Tamiasciurus hudsonicus) to uncover whether selection acts on CORT in natural systems. In this study population, CORT has important fitness implications because this hormone mediates an adaptive maternal effect. First, we use tools from quantitative genetics to (i) calculate the heritability of this trait, and (ii) partition variance in CORT among different possible components (i.e. maternal effect, environmental effect, cohort effect, etc). Second, we use results of an experimental evolution manipulation to determine whether CORT responds to selection in natural systems. This study contributes to evolutionary endocrinology by improving our understanding of how hormonal coping mechanisms arise in free-living populations.
