title: Corticosterone and pace of life in two life-history ecotypes of the garter snake Thamnophis elegans.
abstract: Glucocorticoids are main candidates for mediating life-history trade-offs by regulating the balance between current reproduction and survival. It has been proposed that slow-living organisms should show higher stress-induced glucocorticoid levels that favor self-maintenance rather than current reproduction when compared to fast-living organisms. We tested this hypothesis in replicate populations of two ecotypes of the garter snake (Thamnophis elegans) that exhibit slow and fast pace of life strategies. We subjected free-ranging snakes to a capture-restraint protocol and compared the stress-induced corticosterone levels between slow- and fast-living snakes. We also used a five-year dataset to assess whether baseline corticosterone levels followed the same pattern as stress-induced levels in relation to pace of life. In accordance with the hypothesis, slow-living snakes showed higher stress-induced corticosterone levels than fast-living snakes. Baseline corticosterone levels showed a similar pattern with ecotype, although differences depended on the year of study. Overall, however, levels of glucocorticoids are higher in slow-living than fast-living snakes, which should favor self-maintenance and survival at the expense of current reproduction. The results of the present study are the first to relate glucocorticoid levels and pace of life in a reptilian system and contribute to our understanding of the physiological mechanisms involved in life-history evolution.
authors.affiliation: Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA. mgp@iastate.edu
authors.forename: Maria G
authors.initials: MG
authors.lastname: Palacios
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Sparkman
authors.forename: Anne M
authors.initials: AM
authors.lastname: Bronikowski
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D005075:Biological Evolution; D017812:Colubridae / Q000502:physiology*; D003345:Corticosterone / Q000097:blood*; D060146:Ecotype; D005260:Female; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D003345:Corticosterone