SG: An experimental test of the role of chromosomal inversions in adaptive evolution

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As organisms reproduce and replicate the DNA in their chromosomes, regions of DNA sequence can get reversed relative to that of the original chromosome. Offspring inherit copies of the chromosomes bearing the original or the inverted sequence. In some natural populations, inverted chromosomes can become abundantly distributed. This suggests that they may confer an advantage to the organism that has them. This research will provide the first experimental test of an important hypothesis that would explain why these DNA reversals can proliferate. Inversions often have large effects and are common in many species, including humans. Understanding their persistence and spread is important to basic research and applied research including medicine and agriculture. This project will also support the development of online tools to help teach basic genetics and evolution principles at the high school level.A decade ago, the Kirkpatrick-Barton mathematical model was proposed to explain how natural selection would allow new inversions to spread in natural populations. Although never experimentally verified, this model has been invoked to explain the spread of inversions in a wide variety of species. This project will experimentally test this model using populations of Drosophila melanogaster fruit flies. The researchers will use genome editing tools to experimentally create an inversion that captures alleles known to be associated with adaptations to particular environments. The researchers will monitor the pace with which the chromosomal inversion spreads in replicated experimental populations and compare this pace to detailed model predictions. The results should either provide a strong experimental confirmation of this popular model or identify deviations that would suggest a rethinking of how and why chromosomal inversions spread in natural populations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.