Glucocorticoid-environment relationships align with responses to environmental change in two co-occurring congeners

As more species undergo range shifts in response to climate change, it is increasingly important to understand the factors that determine an organism’s realized niche. Physiological limits imposed by abiotic factors constrain the distributions of many species. Because glucocorticoids are essential to the maintenance of physiological homeostasis, identifying glucocorticoid-environment relationships may generate critical insights into both limits on species distributions and potential responses to environmental change. We explored relationships between variability in baseline glucocorticoids and sensitivity to environmental conditions in two chipmunk species characterized by divergent patterns of spatial, genetic, and morphological change over the past century. Specifically, we investigated whether the alpine chipmunk (Tamias alpinus), which has undergone pronounced changes, displays greater glucocorticoid sensitivity to environmental parameters than the lodgepole chipmunk (T. speciosus),...