Demographic drivers of generation time in a bird metapopulation:
evolutionary potential and the ecological determinants of pace-of-life
Yimen G. Araya-Ajoy1*, Alina K.
Niskanen1,2, Hannah Froy1, Peter
Sjolte Ranke1, Thomas Kvalnes1,
Bernt Rønning1, Michael P.
Pedersen1, Henrik Jensen1, Thor
Harald Ringsby1, Bernt-Erik Sæther1,
Jonathan Wright1
1Centre for Biodiversity Dynamics (CBD), Department of
Biology, Norwegian University of Science and Technology (NTNU), N-7491
Trondheim, Norway.
2Ecology and Genetics Research Unit, University of
Oulu, 90014 Oulu, Finland
*Corresponding author: yimencr@gmail.com
Keywords: life-history theory, trade-offs, density dependence, age
dependence, pace-of-life syndromes, fast-slow axis.
Running title: Pace-of-life in a bird metapopulation
Type of article: letter
Abstract: 150/150 words; main text: 4966 words; references: 45, figures:
2, tables: 4
Data accessibility statement: Data supporting the results will be
archived in Dryad.
Statement of authorship: YAA wrote the first draft of the manuscript,
and all authors contributed substantially to revisions. YAA and JW
designed the study. The study population was established by BES, THR and
HJ. HJ, THR, TK, PSR and BR conducted fieldwork. AN and HJ developed the
pedigree. YAA perform the analyses with input from all co-authors.
Abstract (150/150 words)
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
generation time is a heritable trait and that males have longer
generation times than females. Individuals with longer generation times
contributed to population growth later in life, lived longer and
produced fewer recruits per year. Moreover, these individuals had
greater lifetime reproductive success, but not necessarily higher
expected individual growth rates. 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 density dependence is a key determinant of the pace of
life-history strategies.