350 — The genetic basis of diurnal preference in Drosophila melanogaster

I just stared at my ceiling for five hours, so I guess I’ll just get up out of bed and read a paper about circadian rhythms.

Life inside of a lab is different from life outside of the lab — as any researcher could tell you. But there are also more fundamental, epigenetic changes that take place in a species when it is raised in close proximity to humans (#222). Lab fruit flies tend to be most active during dawn and dusk, but we know that in the wild, fruit flies have a wide variety of phase preference. That is, some tend to be nocturnal, some tend to be diurnal…

Though it’s easy to understand differences in behavior between nocturnal and diurnal variants, it’s not obvious what the genetic underpinnings of this difference are.

In order to learn what genes drive phase preference, these researchers “unnaturally-selected” (artificially selected) for strains of fly that prefer nocturnality or diurnality. In other words, in the strains that were designed to be nocturnal, they found the most nocturnal flies and crossed only those; and likewise, in the diurnal strains, those were the flies that were left out of mating.

Males from the two final populations appeared to be in equal health, but nocturnal females lived longer than their diurnal cousins (crepuscular females fell between the two extremes), and their progeny numbers were greater.

Because the two strains were from the same starting population, it is possible to directly compare their genetics in order to understand what happened over the course of phase preference selection. The authors identified a small number of core genes (most in some way associated with circadian clock output and input) that were, understandably, most dramatically different between the populations. This gives us a very clear forward path to better understand the same genes or their analogs in other species, and better understanding the role that diel phase plays in evolution.