The fact that diurnality preference is usually similar within phylogenetic groups alludes to an underlying genetic mechanism. The genetic basis for such phase preference is largely unknown and is the focus of this study. Selection for activity during a specific time of the day is driven by various factors, including preferred temperature or light intensity, food availability and predation. Most animal species exhibit locomotor activity that is restricted to a defined part of the day, and this preference constitutes the species-specific temporal niche. The diurnal and nocturnal selection strains provide us with a unique opportunity to understand the genetic architecture of diurnal preference.Īlthough time is one of the most important dimensions that define the species ecological niche, it is often a neglected research area. We identified candidate genes associated with diurnality/nocturnality, while data emerging from our expression analysis and behavioural experiments suggest that both clock and clock-independent pathways are involved in shaping diurnal preference. Our study demonstrates that genetic variation segregating in wild populations contributes to substantial variation in diurnal preference. This finding was congruent with behavioural experiments indicating that both light masking and the circadian pacemaker are involved in driving nocturnality. Other than one circadian clock gene ( pdp1), most differentially expressed genes were associated with either clock output ( pdf, to) or input ( Rh3, Rh2, msn). We used whole-genome expression analysis to identify differentially expressed genes in diurnal, nocturnal and crepuscular (control) flies. After 10 generations, we obtained highly diurnal and nocturnal strains. Using a highly diverse population, we performed an artificial selection experiment, selecting flies with extreme diurnal or nocturnal preference. However, a survey of strains derived from wild populations indicated that high variability among individuals exists, including flies that are nocturnal. Under laboratory conditions, Drosophila melanogaster is crepuscular, showing a bi-modal activity profile. The genetic basis underlying diurnal preference is largely unknown. Most animals restrict their activity to a specific part of the day, being diurnal, nocturnal or crepuscular.
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