Independent axes of genetic variation and parallel evolutionary divergence of opercle bone shape in threespine stickleback

Charles B. Kimmel, William A. Cresko, Patrick C. Phillips, Bonnie Ullmann, Mark Currey, Frank Von Hippel, Bjarni K. Kristjánsson, Ofer Gelmond, Katrina McGuigan

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Evolution of similar phenotypes in independent populations is often taken as evidence of adaptation to the same fitness optimum. However, the genetic architecture of traits might cause evolution to proceed more often toward particular phenotypes, and less often toward others, independently of the adaptive value of the traits. Freshwater populations of Alaskan threespine stickleback have repeatedly evolved the same distinctive opercle shape after divergence from an oceanic ancestor. Here we demonstrate that this pattern of parallel evolution is widespread, distinguishing oceanic and freshwater populations across the Pacific Coast of North America and Iceland. We test whether this parallel evolution reflects genetic bias by estimating the additive genetic variance-covariance matrix (G) of opercle shape in an Alaskan oceanic (putative ancestral) population. We find significant additive genetic variance for opercle shape and that G has the potential to be biasing, because of the existence of regions of phenotypic space with low additive genetic variation. However, evolution did not occur along major eigenvectors of G, rather it occurred repeatedly in the same directions of high evolvability. We conclude that the parallel opercle evolution is most likely due to selection during adaptation to freshwater habitats, rather than due to biasing effects of opercle genetic architecture.

Original languageEnglish (US)
Pages (from-to)419-434
Number of pages16
Issue number2
StatePublished - Feb 2012
Externally publishedYes


  • Craniofacial
  • G matrix
  • Gasterosteus aculeatus
  • Genetic basis of traits
  • Genetic bias
  • Genetic constraint
  • Microevolution
  • Quantitative genetics

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • General Agricultural and Biological Sciences


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