Fig. 1

Experimental design: 250 isofemale lines from a natural Drosophila simulans population constituted the ancestral populations. The populations were kept at a constant population size (1000 flies) with non-overlapping generations either in a hot environment (red) fluctuating between 28 and 18 °C on a 12/12 h cycle or a cold environment (blue), fluctuating between 20 and 10 °C (five replicated populations in each environment). We performed multiple phenotypic measurements on the evolved and reconstituted ancestral populations (green) in common garden experiments. We profiled the transcriptome of hot- (F64) and cold- (F39) evolved and reconstituted ancestral populations. Resting metabolism (CO₂ emission) and fecundity were measured later in the experiment (cold-evolved F74–F77; hot-evolved F127–F133). We also sequenced the entire genome of the ancestral and hot-evolved populations (F59)