Long-term measures of climate unpredictability shape the avian endocrine stress axis
Department
Ecology, Evolution, and Organismal Biology
Document Type
Article
Publication Date
9-1-2021
Abstract
The vertebrate glucocorticoid stress response is an important mechanism facilitating pleiotropic phenotypic adjustments for coping with environmental change and optimizing fitness. Although circulating glucocorticoid hormones are mediators of plasticity that individuals can adjust rapidly in response to environmental challenges, they are also shaped by ecological selection. It remains unclear, however, how environmental variation on different timescales influences glucocorticoids. Here, we use an intraspecific comparative approach to determine how variation in precipitation on different timescales (months, years, decades) shapes distinct components of the glucocorticoid response.We sampled superb starlings (Lamprotornis superbus) at eight sites across Kenya in multiple years that differed in precipitation. Among-population variation in baseline glucocorticoids was shaped by both short- and long-term precipitation, whereas variation in stressinduced levels was poorly explained by precipitation on any timescale. Adrenal sensitivity, quantified via adrenocorticotropic hormone injections, was shaped by long-term precipitation and was highest in unpredictable environments. Together, these results suggest that variation in glucocorticoids can be best explained by environmental variation at timescales that extend beyond the lives of individuals, although baseline glucocorticoids also reflect short-term environmental conditions. Patterns of long-term precipitation may represent amicroevolutionary selective pressure shaping the endocrine stress axis across populations and influencing how individuals cope with environmental change.
Journal Title
American Naturalist
Journal ISSN
00030147
Volume
198
Issue
3
First Page
394
Last Page
405
Digital Object Identifier (DOI)
10.1086/715628