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.