Variation in shape and consistency of selection between populations of the threatened Hihi ( <i>Notiomystis cincta</i> )

International audienceEnvironmental variation is a fundamental aspect of evolution: fluctuations in environmental conditions over time can generate fluctuations in natural selection, which in turn can shape phenotypic variation (Darwin, 1859). The theoretical relationship between fluctuating selection and phenotypic variation has been well-studied, notably through moving optimum models. In such models, selection favours an optimal trait value that varies over time, in turn favouring new phenotypes that better match with the new optimum of fitness (Kopp & Matuszewski, 2014). When this variation is stochastic (rather than a single sudden or a gradual change of the optimum), the changing environment is expected to induce a continual change in selection direction and intensity, leading to fluctuations in the optimal phenotype over time (Chevin et al., 2017; Estes & Arnold, 2007; Matuszewski et al., 2014). Moving optimum models have emphasized the importance of stochastic environmental variation in the maintenance of phenotypic heterogeneity via genetic polymorphis