Tracking changes in chromosomal arrangements and their genetic content during adaptation

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Chromosomal inversions are known to have adaptive roles, but their genetic evolution and impact on chromosomal polymorphism are debated.
• Understanding how inversions change and influence adaptation is crucial for evolutionary biology.

Purpose of the Study:

• To investigate the evolution of genetic content within chromosomal inversions.
• To link changes in inversions to adaptation and chromosomal polymorphism in Drosophila subobscura.
• To determine the role of genetic changes within inversions in adaptation.

Main Methods:

• Laboratory evolution experiment with three replicate populations of Drosophila subobscura over 30 generations.
• Monitoring of life-history traits, chromosomal arrangements, and 22 microsatellites within and outside inversions.
• Analysis of allele frequency changes, linkage disequilibrium, and evidence of selection.

Main Results:

• Adaptation to a new environment was observed, alongside directional evolution of chromosomal polymorphism.
• Selective changes in the frequency of seven out of 23 chromosomal arrangements were detected, supporting the adaptive role of inversions.
• Evidence suggests adaptive changes in inversion genetic content, with some microsatellite alleles increasing in frequency within inversions due to selection, potentially via hitchhiking.

Conclusions:

• Genetic changes within chromosomal inversions significantly contribute to adaptation.
• Selection acts on the genetic content of inversions, influencing their evolution and the broader landscape of chromosomal polymorphism.
• The study provides evidence for the dynamic evolution of inversions and their genetic material during adaptation.