title: Environmental variability and the evolution of the glucocorticoid receptor (Nr3c1) in African starlings.
abstract: One of the primary ways that organisms cope with environmental change is through regulation of the hypothalamo-pituitary-adrenal (HPA) axis, the neuroendocrine system that controls reactions to stress. Variation in genes regulating the HPA axis - particularly the glucocorticoid receptor - may facilitate adaptation to changing climatic conditions by altering expression. Here we examine signatures of selection on the glucocorticoid receptor gene (Nr3c1) in African starlings that inhabit a range of environments, including those with variable climatic conditions. To investigate potential adaptive mechanisms underlying the vertebrate stress response, we sequence the Nr3c1 gene in 27 species of African starlings. Although we find some evidence of positive selection, substitution rate is negatively correlated with variance in precipitation. This suggests climatic cycling in sub-Saharan Africa may have resulted in lower substitution rates to maintain a successful coping strategy. When environmental conditions fluctuate rapidly, variation in the strength of purifying selection can explain evolutionary rate variation.
authors: Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, NY, 10027, USA. nrh44@cornell.edu.
authors: Natalie R
authors: 0000-0002-6875-412X
authors: NR
authors: Hofmeister
authors: Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, NY, 10027, USA.|Center for Integrative Animal Behavior, Columbia University, 1200 Amsterdam Avenue, New York, NY, 10027, USA.
authors: Dustin R
authors: DR
authors: Rubenstein
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D017753:Ecosystem; D019143:Evolution, Molecular; D046109:Passeriformes / Q000235:genetics* / Q000502:physiology*; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*
chemical_list: D011965:Receptors, Glucocorticoid
keywords: Adaptation; canalisation; environmental variability; fluctuating selection; stress response