Correlated changes in circadian clocks in response to selection for faster pre-adult development in fruit flies Drosophila melanogaster.

Although, circadian clocks are believed to be involved in the regulation of life-history traits such as pre-adult development time and lifespan in fruit flies Drosophila melanogaster, there is very little unequivocal evidence either to support or refute this. Here we report the results of a long-term study aimed at examining the role of circadian clocks in the temporal regulation of pre-adult development in D. melanogaster. We employed laboratory selection protocol for faster pre-adult development on four large, outbred, random mating populations of Drosophila. We assayed pre-adult development time and circadian period of locomotor activity rhythm of these flies at regular intervals of 5-10 generations. After 50 generations of selection, the overall egg-to-adult duration in the selected stocks was reduced by ~29 h (~12.5%) relative to controls, with the selected populations showing a concurrent reduction in time taken to hatching, pupation and wing pigmentation, by ~2, ~16, and ~25.2 h, respectively. Furthermore, selected populations showed a concomitant reduction in the circadian period of locomotor activity rhythm, implying that circadian clocks and development time are correlated. Thus, our study provides the first ever unequivocal evidence for the evolution of circadian clocks as a correlated response to selection for faster pre-adult development, suggesting that circadian clocks and development are linked in fruit flies D. melanogaster.