Genotype‐by‐environment Interactions for Fitness of Erigeron Annuus Show Fine‐scale Selective Heterogeneity

The results of natural selection depend critically on whether variation in fitness is finegrained or coarse-grained with respect to dispersal, but little is known of the spatial scale of fitness variation in natural populations. For most evolutionary questions, environmental heterogeneity must be defined by reversals in the relative fitness of genotypes; absolute fitness may vary, but if genotypes respond in parallel then selection is uniform. Thus, measurements of genotype-by-environment (G × E) interactions for fitness are necessary to understand patterns of variation in natural selection.