Sex-specific additive genetic variances and correlations for fitness in a song sparrow (Melospiza melodia) population subject to natural immigration and inbreeding

Matthew E. Wolak* (Corresponding Author), Peter Arcese, Lukas F. Keller, Pirmin Nietlisbach, Jane M. Reid* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)
15 Downloads (Pure)


Quantifying sex-specific additive genetic variance (VA) in fitness, and the cross-sex genetic correlation (rA), is prerequisite to predicting evolutionary dynamics and the magnitude of sexual conflict. Further, quantifying VA and rA in underlying fitness components, and genetic consequences of immigration and resulting gene flow, is required to identify mechanisms that maintain VA in fitness. However, these key parameters have rarely been estimated in wild populations experiencing natural environmental variation and immigration. We used comprehensive pedigree and life history data from song sparrows (Melospiza melodia) to estimate VA and rA in sex-specific fitness and underlying fitness components, and to estimate additive genetic effects of immigrants alongside inbreeding depression. We found evidence of substantial VA in female and male fitness, with a moderate positive cross-sex rA. There was also substantial VA in male but not female adult reproductive success, and moderate VA in juvenile survival but not adult annual survival. Immigrants introduced alleles with negative additive genetic effects on local fitness, potentially reducing population mean fitness through migration load, but alleviating expression of inbreeding depression. Our results show that VA for fitness can be maintained in the wild, and be broadly concordant between the sexes despite marked sex-specific VA in reproductive success.
Original languageEnglish
Pages (from-to)2057-2075
Number of pages18
Issue number10
Early online date24 Sept 2018
Publication statusPublished - Oct 2018

Bibliographical note


We thank the Tsawout and Tseycum First Nation bands for access to Mandarte and everyone who contributed to the long-term data collection. We thank the European Research Council for funding and the University of Aberdeen for generous access to the Maxwell High Performance Computing cluster. Pierre de Villemereuil, Michael B. Morrissey, and Jarrod D. Hadfield provided enlightening discussions during manuscript preparation. Joel McGlothlin and two anonymous reviewers provided further helpful comments.


Data have been archived in the Dryad Digital Repository: (Wolak et al. 2018).


  • Cross-sex genetic correlation
  • genetic groups
  • inbreeding depression
  • migration load
  • quantitative genetic generalized linear mixed model
  • sexual conflict


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