Variation within and among species in gene expression: Raw material for evolution

Andrew Whitehead, Douglas L. Crawford

Research output: Contribution to journalReview articlepeer-review

261 Scopus citations


Heritable variation in regulatory or coding regions is the raw material for evolutionary processes. The advent of microarrays has recently promoted examination of the extent of variation in gene expression within and among taxa and examination of the evolutionary processes affecting variation. This review examines these issues. We find: (i) microarray-based measures of gene expression are precise given appropriate experimental design; (ii) there is large inter-individual variation, which is composed of a minor nongenetic component and a large heritable component; (iii) variation among populations and species appears to be affected primarily by neutral drift and stabilizing selection, and to a lesser degree by directional selection; and (iv) neutral evolutionary divergence in gene expression becomes nonlinear with greater divergence times due to functional constraint. Evolutionary analyses of gene expression reviewed here provide unique insights into partitioning of regulatory variation in nature. However, common limitations of these studies include the tendency to assume a linear relationship between expression divergence and species divergence, and failure to test explicit hypotheses that involve the ecological context of evolutionary divergence.

Original languageEnglish (US)
Pages (from-to)1197-1211
Number of pages15
JournalMolecular ecology
Issue number5
StatePublished - Apr 2006


  • Comparative biology
  • Evolution
  • Functional genomics
  • Gene expression
  • Genetic drift
  • Microarrays
  • Natural selection

ASJC Scopus subject areas

  • Ecology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry


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