Extensive local adaptation within the chemosensory system following Drosophila melanogaster’s global expansion

TLDR

Adaptation to new environments is a fundamental biological question that remains poorly understood at the genetic level, and chemosensory systems—linking external signals to internal responses—offer a compelling model for study. The study aims to determine how natural selection has shaped the chemosensory system of *Drosophila melanogaster* by analyzing genome‑wide data from five diverse populations. The authors performed genome‑wide population genetic analyses across five diverse *Drosophila melanogaster* populations to detect signatures of selection in chemosensory genes. Chemo‑sensory proteins are not outliers for adaptive divergence between species, yet they frequently show the strongest genome‑wide signals of recent selection within *D.

Abstract

Abstract How organisms adapt to new environments is of fundamental biological interest, but poorly understood at the genetic level. Chemosensory systems provide attractive models to address this problem, because they lie between external environmental signals and internal physiological responses. To investigate how selection has shaped the well-characterized chemosensory system of Drosophila melanogaster , we have analysed genome-wide data from five diverse populations. By couching population genomic analyses of chemosensory protein families within parallel analyses of other large families, we demonstrate that chemosensory proteins are not outliers for adaptive divergence between species. However, chemosensory families often display the strongest genome-wide signals of recent selection within D. melanogaster . We show that recent adaptation has operated almost exclusively on standing variation, and that patterns of adaptive mutations predict diverse effects on protein function. Finally, we provide evidence that chemosensory proteins have experienced relaxed constraint, and argue that this has been important for their rapid adaptation over short timescales.