Population genomic structure of a widespread, urban-dwelling mammal: The eastern grey squirrel (Sciurus carolinensis)

Nicole A. Fusco, Bradley J. Cosentino, James P. Gibbs, Maximilian L. Allen, Alexander J. Blumenfeld, George H. Boettner, Elizabeth J. Carlen, Merri Collins, Catherine Dennison, Devin DiGiacopo, André Philippe Drapeau Picard, Jonathan Edmonson, M. Caitlin Fisher-Reid, Rebecca Fyffe, Travis Gallo, Alannah Grant, William Harbold, Stephen B. Heard, Diana J.R. Lafferty, Richard M. LehtinenShealyn Marino, John E. McDonald, Alessio Mortelliti, Maureen Murray, Amy Newman, Krista N. Oswald, Caitlin Ott-Conn, Jonathan L. Richardson, Rebecca Rimbach, Paul Salaman, Michael Steele, Mason R. Stothart, Mark C. Urban, Kurt Vandegrift, John P. Vanek, Sean N. Vanderluit, Lucie Vezina, Adalgisa Caccone

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Urbanization is a persistent and widespread driver of global environmental change, potentially shaping evolutionary processes due to genetic drift and reduced gene flow in cities induced by habitat fragmentation and small population sizes. We tested this prediction for the eastern grey squirrel (Sciurus carolinensis), a common and conspicuous forest-dwelling rodent, by obtaining 44K SNPs using reduced representation sequencing (ddRAD) for 403 individuals sampled across the species' native range in eastern North America. We observed moderate levels of genetic diversity, low levels of inbreeding, and only a modest signal of isolation-by-distance. Clustering and migration analyses show that estimated levels of migration and genetic connectivity were higher than expected across cities and forested areas, specifically within the eastern portion of the species' range dominated by urbanization, and genetic connectivity was less than expected within the western range where the landscape is fragmented by agriculture. Landscape genetic methods revealed greater gene flow among individual squirrels in forested regions, which likely provide abundant food and shelter for squirrels. Although gene flow appears to be higher in areas with more tree cover, only slight discontinuities in gene flow suggest eastern grey squirrels have maintained connected populations across urban areas in all but the most heavily fragmented agricultural landscapes. Our results suggest urbanization shapes biological evolution in wildlife species depending strongly on the composition and habitability of the landscape matrix surrounding urban areas.

Original languageEnglish
Article numbere17230
JournalMolecular Ecology
Issue number3
StatePublished - 1 Feb 2024


  • Sciurus carolinensis
  • contemporary evolution
  • ddRAD
  • eastern grey squirrel
  • evolution
  • gene flow
  • habitat fragmentation
  • population genomics
  • population structure
  • urbanization

ASJC Scopus subject areas

  • Genetics
  • Ecology, Evolution, Behavior and Systematics


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