Multilevel and sex‐specific selection on competitive traits in North American red squirrels

David N. Fisher* (Corresponding Author), Stan Boutin, Ben Dantzer, Murray M. Humphries, Jeffrey E. Lane, Andrew G. McAdam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Individuals often interact more closely with some members of the population (e.g., offspring, siblings, or group members) than they do with other individuals. This structuring of interactions can lead to multilevel natural selection, where traits expressed at the group‐level influence fitness alongside individual‐level traits. Such multilevel selection can alter evolutionary trajectories, yet is rarely quantified in the wild, especially for species that do not interact in clearly demarcated groups. We quantified multilevel natural selection on two traits, postnatal growth rate and birth date, in a population of North American red squirrels (Tamiasciurus hudsonicus). The strongest level of selection was typically within‐acoustic social neighborhoods (within 130 m of the nest), where growing faster and being born earlier than nearby litters was key, while selection on growth rate was also apparent both within‐litters and within‐study areas. Higher population densities increased the strength of selection for earlier breeding, but did not influence selection on growth rates. Females experienced especially strong selection on growth rate at the within‐litter level, possibly linked to the biased bequeathal of the maternal territory to daughters. Our results demonstrate the importance of considering multilevel and sex‐specific selection in wild species, including those that are territorial and sexually monomorphic.
Original languageEnglish
Pages (from-to)1841-1854
Number of pages14
Issue number7
Early online date8 Jun 2017
Publication statusPublished - Jul 2017

Bibliographical note

We thank Agnes Moose and her family for long-term access to hertrapline, and to the Champagne and Aishihik First Nations for allowing us to conduct work on their land. We thank all the volunteers, field assistants,and graduate students whose tireless work makes the KRSP possible. We have no conflicts of interest. This is KRSP paper number 83. Funding for this study was provided by the Natural Sciences and Engineering Research Council, the Northern Scientific Training Program, the National Science Foundation, and the Ontario Ministry of Research and Innovation.


  • KRSP
  • multilevel selection
  • natural selection
  • North American red squirrel
  • selection coefficient
  • spatial scale
  • ami-asciurus hudsonicus


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