Individuals differ in average phenotypes and in sensitivity to environmental variation. Such context sensitivity can be modelled as random slope variation. Random slope variation implies that the proportion of between-individual variation varies across the range of a covariate (environment/context/time/age) and has thus been called ‘conditional’ repeatability. We propose to put conditional repeatabilities in perspective of the total phenotypic variance and suggest a way of standardization using the random slope coefficient of determination (Formula presented.). Furthermore, we illustrate that the marginalized repeatability (Formula presented.) averaged across an environmental gradient offers a biologically relevant description of between-individual variation. We provide simple equations for calculating key descriptors of conditional repeatabilities, clarify the difference between random intercept variation and average between-individual variation and make recommendations for comprehensive reporting. While we introduce the concept with individual variation in mind, the framework is equally applicable to other type of between-group/cluster variation that varies across some (environmental) gradient.
CITATION STYLE
Schielzeth, H., & Nakagawa, S. (2022). Conditional repeatability and the variance explained by reaction norm variation in random slope models. Methods in Ecology and Evolution, 13(6), 1214–1223. https://doi.org/10.1111/2041-210X.13856
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