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Demographic drivers of generation time in a bird metapopulation: evolutionary potential and the ecological determinants of pace-of-life
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  • Yimen Araya-Ajoy,
  • Alina Niskanen,
  • Peter Ranke,
  • Hannah Froy,
  • Thomas Kvalnes,
  • Bernt Rønning,
  • Michael Pedersen,
  • Thor-Harald Ringsby,
  • Henrik Jensen,
  • Bernt-Erik Sæther,
  • Jonathan Wright
Yimen Araya-Ajoy
Norwegian University of Science and Technology
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Alina Niskanen
University of Oulu
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Peter Ranke
Norwegian University of Science and Technology
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Hannah Froy
Norwegian University of Science and Technology
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Thomas Kvalnes
Norwegian University of Science and Technology
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Bernt Rønning
Norwegian University of Science and Technology
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Michael Pedersen
Norwegian University of Science and Technology
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Thor-Harald Ringsby
Norwegian University of Science and Technology
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Henrik Jensen
Norwegian University of Science and Technology
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Bernt-Erik Sæther
Centre for Biodiversity Dynamics
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Jonathan Wright
NTNU
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Abstract

Generation time determines the pace of key demographic and evolutionary processes. Quantified as the weighted mean age at reproduction, it can be studied as a trait that may evolve and change in response to ecological conditions. We combined quantitative genetic analyses of individual projection matrices with age- and density-dependent models to study generation time variation in a bird metapopulation. We found that males have longer generation times than females and that it is a heritable trait. Individuals with longer generation times contributed to population growth later in life, lived longer, produced fewer recruits per year, had greater lifetime reproductive success, but not necessarily a higher expected individual growth rate. As predicted by density-dependence theory, generation times were shorter when populations were growing, and longer when populations were closer to equilibrium or declining. These results support classic theory predicting that competitive regimes are key determinants of the pace of life-history strategies.