title: Within-individual plasticity explains age-related decrease in stress response in a short-lived bird.
abstract: A crucial problem for every organism is how to allocate energy between competing life-history components. The optimal allocation decision is often state-dependent and mediated by hormones. Here, we investigated how age, a major state variable affects individuals' hormonal response to a standardized stressor: a trait that may reflect allocation between self-maintenance and reproduction. We caught free-living house sparrows and measured their hormonal (corticosterone) response to capture stress in consecutive years. Using a long-term ringing dataset, we determined the age of the birds, and we partitioned the variation into within- and among-individual age components to investigate the effects of plasticity versus selection or gene flow, respectively, on the stress response. We found large among-individual variation in the birds' hormone profiles, but overall, birds responded less strongly to capture stress as they grew older. These results suggest that stress responsiveness is a plastic trait that may vary within individuals in an adaptive manner, and natural selection may act on the reaction norms producing optimal phenotypic response in the actual environment and life-history stage.
authors.affiliation: Department of Evolutionary Zoology and Human Biology, University of Debrecen, Egyetem tér 1, Debrecen 4032, Hungary lendvai@nyf.hu.
authors.forename: Ádám Z
authors.identifier: http://orcid.org/0000-0002-8953-920X
authors.initials: ÁZ
authors.lastname: Lendvai
authors.affiliation: School of Biological Sciences, The University of Sydney, Heydon-Laurence Building A08, New South Wales 2006, Australia.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Giraudeau
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, Budapest 1022, Hungary.
authors.forename: Veronika
authors.identifier: http://orcid.org/0000-0002-2136-5346
authors.initials: V
authors.lastname: Bókony
authors.affiliation: Centre d'Etudes Biologiques de Chizé, UMR 7372 CNRS-Université de la Rochelle, La Rochelle, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Angelier
authors.affiliation: Centre d'Etudes Biologiques de Chizé, UMR 7372 CNRS-Université de la Rochelle, La Rochelle, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
mesh_terms: D000367:Age Factors; D000818:Animals; D003345:Corticosterone / Q000097:blood*; D005602:France; D046370:Sparrows / Q000097:blood / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D003345:Corticosterone
keywords: corticosterone; plasticity; stress response