Variation in reaction norms: statistical considerations and biological interpretation

Michael Blair Morrissey, Maartje Liefting

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)
3 Downloads (Pure)


Analysis of reaction norms, the functions by which the phenotype produced by a given genotype depends on the environment, is critical to studying many aspects of phenotypic evolution. Different techniques are available for quantifying different aspects of reaction norm variation. We examine what biological inferences can be drawn from some of the more readily-applicable analyses for studying reaction norms. We adopt a strongly biologically-motivated view, but draw on statistical theory to highlight strengths and drawbacks of different techniques. In particular, consideration of some formal statistical theory leads to revision of some recently, and forcefully, advocated opinions on reaction norm analysis. We clarify what simple analysis of the slope between mean phenotype in two environments can tell us about reaction norms, explore the conditions under which polynomial regression can provide robust inferences about reaction norm shape, and explore how different existing approaches may be used to draw inferences about variation in reaction norm shape. We show how mixed model-based approaches can provide more robust inferences than more commonly-used multistep statistical approaches, and derive new metrics of the relative importance of variation in reaction norm intercepts, slopes, and curvatures.
Original languageEnglish
Pages (from-to)1944-1959
Number of pages16
Issue number9
Early online date21 Aug 2016
Publication statusPublished - 7 Sept 2016


  • Phenotypic plasticity
  • Reaction norm
  • Statistics


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