Adaptation of Circadian Neuronal Network to Photoperiod in High-Latitude European Drosophilids

The genus Drosophila contains over 2,000 species that, stemming from a common ancestor in the Old World Tropics, populate today very different environments [1, 2] (reviewed in [3]). We found significant differences in the activity pattern of Drosophila species belonging to the holarctic virilis group, i.e., D. ezoana and D. littoralis, collected in Northern Europe, compared to that of the cosmopolitan D. melanogaster, collected close to the equator. These behavioral differences might have been of adaptive significance for colonizing high-latitude habitats and hence adjust to long photoperiods. Most interestingly, the flies’ locomotor activity correlates with the neurochemistry of their circadian clock network, which differs between low and high latitude for the expression pattern of the blue light photopigment cryptochrome (CRY) and the neuropeptide Pigment-dispersing factor (PDF) [4–6]. In D. melanogaster, CRY and PDF are known to modulate the timing of activity and to maintain robust rhythmicity under constant conditions [7–11]. We could partly simulate the rhythmic behavior of the high-latitude virilis group species by mimicking their CRY/PDF expression patterns in a laboratory strain of D. melanogaster. We therefore suggest that these alterations in the CRY/PDF clock neurochemistry might have allowed the virilis group species to colonize high-latitude environments. [Display omitted] •This is the first detailed analysis of fruit fly daily activity under long days•D. ezoana and D. littoralis circadian clock differ from that of D. melanogaster•In flies, CRY and PDF are essential for adapting to long days•Changing CRY/PDF distribution in melanogaster mimics northern species daily activity The circadian clock modulates daily activity. Menegazzi et al. found a functional link between the clock neurochemistry of fruit flies species and their ability to adjust activity to long summer days. The expression pattern of clock components in northern species might be of advantage for life in the north.