Evolutionary stasis of a heritable morphological trait in a wild fish population despite apparent directional selection

Ronan James O'Sullivan, Tutku Aykanat, Susan E Johnston, Adam Kane, Russell Poole, Ger Rogan, Paulo A Prodöhl, Craig R Primmer, Philip McGinnity, Thomas Eric Reed

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Comparing observed versus theoretically expected evolutionary responses is important for our understanding of the evolutionary process, and for assessing how species may cope with anthropogenic change. Here, we document directional selection for larger female size in Atlantic salmon, using pedigree-derived estimates of lifetime reproductive success as a fitness measure. We show the trait is heritable and, thus, capable of responding to selection. The Breeder's Equation, which predicts microevolution as the product of phenotypic selection and heritability, predicted evolution of larger size. This was at odds, however, with the observed lack of either phenotypic or genetic temporal trends in body size, a so-called "paradox of stasis." To investigate this paradox, we estimated the additive genetic covariance between trait and fitness, which provides a prediction of evolutionary change according to Robertson's secondary theorem of selection (STS) that is unbiased by missing variables. The STS prediction was consistent with the observed stasis. Decomposition of phenotypic selection gradients into genetic and environmental components revealed a potential upward bias, implying unmeasured factors that covary with trait and fitness. These results showcase the power of pedigreed, wild population studies-which have largely been limited to birds and mammals-to study evolutionary processes on contemporary timescales.
Original languageEnglish
Pages (from-to)7096-7111
Number of pages16
JournalEcology and Evolution
Issue number12
Early online date11 Jun 2019
Publication statusE-pub ahead of print - 11 Jun 2019

Keywords / Materials (for Non-textual outputs)

  • atlantic salmon
  • Breeder's equation
  • pedigree
  • phenotypic selection
  • secondary theorem of selection


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