Independence among physiological traits suggests flexibility in the face of ecological demands on phenotypes

Authors

  • D. M. BUEHLER,

    1. Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
    2. Natural History, Royal Ontario Museum, Toronto, Ontario, Canada
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  • F. VÉZINA,

    1. Département de Biologie, Chimie et Géographie, Groupe de recherche sur les environnements nordiques BORÉAS, Centre d’études nordiques, Université du Québec à Rimouski, Rimouski, Québec, Canada
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  • W. GOYMANN,

    1. Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Seewiesen, Germany
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  • I. SCHWABL,

    1. Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Seewiesen, Germany
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  • M. VERSTEEGH,

    1. Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands
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  • B. I. TIELEMAN,

    1. Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands
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  • T. PIERSMA

    1. Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands
    2. Department of Marine Ecology, Royal Netherlands Institute for Sea Research (NIOZ), Texel, The Netherlands
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Deborah Buehler, Office of the Vice President, Research 12 Queen’s Park Crescent, Toronto, ON, M5S 1S8.
Tel.: +1 416 978 3205; fax: +1 416 946 3707; e-mail: d.buehler@utoronto.ca

Abstract

Phenotypic flexibility allows animals to adjust their physiology to diverse environmental conditions encountered over the year. Examining how these varying traits covary gives insights into potential constraints or freedoms that may shape evolutionary trajectories. In this study, we examined relationships among haematocrit, baseline corticosterone concentration, constitutive immune function and basal metabolic rate in red knot Calidris canutus islandica individuals subjected to experimentally manipulated temperature treatments over an entire annual cycle. If covariation among traits is constrained, we predict consistent covariation within and among individuals. We further predict consistent correlations between physiological and metabolic traits if constraints underlie species-level patterns found along the slow-fast pace-of-life continuum. We found no consistent correlations among haematocrit, baseline corticosterone concentration, immune function and basal metabolic rate either within or among individuals. This provides no evidence for constraints limiting relationships among these measures of the cardiovascular, endocrine, immune and metabolic systems in individual red knots. Rather, our data suggest that knots are free to adjust individual parts of their physiology independently. This makes good sense if one places the animal within its ecological context where different aspects of the environment might put different pressures on different aspects of physiology.

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