title: Breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic Gambel's white-crowned sparrow.
abstract: Individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. Recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. Several studies have found differences in the hypothalamic-pituitary-adrenal (HPA) axis activity in response to acute restraint stress in individuals at the range limits. HPA axis activation leads to elevations in glucocorticoids that regulate physiology and behavior. Here we compare the hormonal profiles and morphometrics from Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) breeding at the northern limit of the population's range to those birds breeding within the historic population range. Birds breeding at the northern limit experienced a harsher environment with colder temperatures; however, we found no differences in arthropod prey biomass between the northern limit and more southern (historic) sites. Males at the northern limit had higher body condition scores (mass corrected for body size) compared to individuals within the historic range, but no differences were found in beak and tarsus lengths, wing chord, muscle profile or fat stores. In males during the pre-parental stage, before breeding commenced, HPA axis activity was elevated in birds at the northern limit of the range, but no differences were found during the parental or molt stages. Females showed no differences in HPA axis activity during the parental stage. This study suggests that "pioneering" individuals at the limits of their breeding range exhibit physiology and morphology that are distinct from individuals within the historic range.
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA. jskrause@ucdavis.edu.
authors.forename: Jesse S
authors.initials: JS
authors.lastname: Krause
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Chmura
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Pérez
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Lisa N
authors.initials: LN
authors.lastname: Quach
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, TX, 76019, USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Asmus
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Karen R
authors.initials: KR
authors.lastname: Word
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Michaela A
authors.initials: MA
authors.lastname: McGuigan
authors.affiliation: Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA.
authors.forename: Shannan K
authors.initials: SK
authors.lastname: Sweet
authors.affiliation: Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, Scotland, UK.
authors.forename: Simone L
authors.initials: SL
authors.lastname: Meddle
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, TX, 76019, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Gough
authors.affiliation: Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA.
authors.forename: Natalie
authors.initials: N
authors.lastname: Boelman
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Wingfield
mesh_terms: D025041:Animal Migration; D000818:Animals; D001110:Arctic Regions; D001947:Breeding; D057231:Climate Change; D003080:Cold Temperature; D003345:Corticosterone / Q000378:metabolism; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism; D006702:Homing Behavior; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D008297:Male; D010641:Phenotype; D010913:Pituitary-Adrenal System / Q000502:physiology*; D012098:Reproduction; D046370:Sparrows / Q000033:anatomy & histology / Q000502:physiology; D013312:Stress, Physiological
chemical_list: D005938:Glucocorticoids; D003345:Corticosterone
keywords: Adrenocortical; Allostatic load; Climate change; Corticosterone; Glucocorticoids; Hypothalamic–pituitary–adrenal axis; Morphometrics