Figure 4From: Evidence that natural selection maintains genetic variation for sleep in Drosophila melanogaster Geographic variation in sunrise anticipation. Percentage of maximal activity across time (= late night activity level) was a normalization of each line’s activity profile between 0 and 1. The data were then averaged over lines for each population. R-squares were obtained at each circadian timepoint from the regression of population mean activity levels over latitude.Back to article page