Geographic and seasonal variation of theforgene reveal signatures of local adaptation inDrosophila melanogaster

Abstract

In the early 1980s, the observation thatDrosophila melanogasterlarvae differed in their foraging behavior laid the foundation for the work that would later lead to the discovery of theforgene and its associated foraging phenotypes, rover and sitter. Since then, the molecular characterization of theforgene and our understanding of the mechanisms that maintain its allelic variants in the laboratory have progressed enormously. However, the significance and dynamics of such variation are yet to be investigated in nature. With the advent of next-generation sequencing, it is now possible to identify loci underlying adaptation of populations in response to environmental variation. Here, I present results of the first genotype-environment association analysis that quantifies variation in theforgene among samples ofD. melanogasterstructured across space and time. These samples consist of published genomes of adult flies collected worldwide, and at least twice per site of collection (during spring and fall). An analysis of genetic differentiation based on Fst and individual admixture estimates revealed an east-west gradient in population structure. The results indicate that different patterns of gene flow as expected under models of isolation by environment and isolation by distance are likely driving the genetic differentiation among populations. Overall, this study is essential for understanding the mechanisms underlying the evolution of foraging behavior inD. melanogaster.