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Bigger is not always better: selection on body mass varies across life stages in a hibernating mammal
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  • Alexandra Jebb,
  • Daniel Blumstein,
  • Julien Martin,
  • Pierre Bize
Alexandra Jebb
University of Aberdeen

Corresponding Author:[email protected]

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Daniel Blumstein
University of California LA
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Julien Martin
University of Ottawa
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Pierre Bize
University of Aberdeen
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Body mass is often viewed as a proxy of past access to resources and of future survival and reproductive success. Links between body mass and survival or reproduction are, however, likely to differ between age classes and sexes. Remarkably, this is rarely taken into account in selection analyses. Selection on body mass is likely to be the primary target accounting for juvenile survival until reproduction but may weaken after recruitment. Males and females also often differ in how they use resources for reproduction and survival. Using a long-term study on yellow-bellied marmots (Marmota flaviventer), we show that body mass was under stabilizing selection in the first years of life, before recruitment, which changed to positive directional selection as age increased and animals matured. We found no evidence that selection across age-classes on body mass differed between sexes. By investigating the link between running speed and body mass, we show that the capacity to escape predators was not consistent across age classes and followed a quadratic relationship at young ages only. Overall, our results indicate that mature age classes exhibit traditional patterns of positive selection on body mass, as expected in a hibernating mammal, but that mass in the first years of life is subject to stabilizing selection which may come from additional predation pressures that negate the benefits of the largest body masses. Our study highlights the importance to disentangle selection pressures on traits across critical age (or life) classes.
14 Jul 2020Submitted to Ecology and Evolution
15 Jul 2020Submission Checks Completed
15 Jul 2020Assigned to Editor
16 Jul 2020Reviewer(s) Assigned
19 Aug 2020Review(s) Completed, Editorial Evaluation Pending
21 Aug 2020Editorial Decision: Revise Minor
30 Nov 20201st Revision Received
01 Dec 2020Submission Checks Completed
01 Dec 2020Assigned to Editor
01 Dec 2020Review(s) Completed, Editorial Evaluation Pending
01 Dec 2020Reviewer(s) Assigned
18 Dec 2020Editorial Decision: Accept
Apr 2021Published in Ecology and Evolution volume 11 issue 7 on pages 3435-3445. 10.1002/ece3.7304