Natural populations of flies that carry the major temperate haplotype (T/T/C/A) manifest decreased daytime sleep compared to the major tropical haplotype (C/A/T/T).

(A-C) Adult male flies from the 42 different populations analyzed in this study (see S1 Appendix and S5 Fig) were kept at 25°C and entrained for five days of LD. For each isofemale line, the locomotor activity of individual flies (n = 16) was measured and data from the last three days of LD pooled to obtain values for the total amount of sleep during the 12 hr of day and the 12 hr of night. Data from the different populations was pooled in different ways to generate the following temperate-tropical comparisons; (A) all 42 populations, (B) SNP3A (30 populations) versus SNP3G (12 populations), and (C) C/A/T/T (11 populations) versus T/T/C/A (9 populations). **, p p values were obtained using one-sided Student’s t-test; [panel A; temperate vs tropical; day, p = 0.0005; night, p = 0.069], [panel B, temperate vs tropical during the day; SNP3A, p p p p p p = 0.0004], [panel C; tropical C/A/T/T vs tropical T/T/C/A during the night; p = 0.36; temperate C/A/T/T vs temperate T/T/C/A during the night; p = 0.28].