Meeting Abstract

30.5  Sunday, Jan. 5 10:30  How does selection act on endocrine traits? And how can we measure it? BONIER, F*; MARTIN, PR; Queen’s University; Queen’s University bonierf@queensu.ca

Behavioral endocrinologists are becoming increasingly interested in the evolutionary context of the endocrine traits that we study. Yet, we lack a robust approach for detecting natural selection on these exquisitely plastic traits, perhaps in large part because of their plasticity, and also because of the complex ways in which selection might act. For example, selection may favor hormone levels that closely match dynamic environmental challenges in nature, and thus optimal phenotypes cannot be understood without accounting for the current and prior challenges facing individuals. I will explore some of the unique challenges for understanding the evolution of endocrine traits, illustrating these challenges using corticosterone levels and life history data from free-ranging birds. Within individual birds, we see fluctuations in relative corticosterone levels depending on diverse challenges — individuals with the highest fitness may have both the highest and lowest levels of corticosterone in the population, depending on the environmental challenges that they face. Overall, standard fitness-trait curves can be misleading, obscuring our understanding of how selection acts on endocrine traits. Reaction norms and adaptive plasticity, however, could provide more useful frameworks for moving forward.