Genetic redundancy fuels polygenic adaptation in Drosophila

Area of Science:

• Evolutionary biology
• Genetics
• Population genetics

Background:

• Adaptive traits are crucial for predicting evolutionary responses.
• Most adaptive traits are polygenic, but identifying small allele frequency changes across many loci is challenging.
• Previous research often focused on traits with simple genetic bases.

Purpose of the Study:

• To investigate the genetic architecture of adaptive traits under laboratory natural selection.
• To detect signatures of selective sweeps and polygenic adaptation.
• To understand the role of genetic redundancy in rapid evolutionary responses.

Main Methods:

• Exposed 10 replicates of Drosophila simulans to a new temperature regime.
• Analyzed genomic data to detect signatures of selection and polygenic adaptation.
• Compared experimental results with simulations assuming different evolutionary paradigms.

Main Results:

• Uncovered a polygenic architecture for an adaptive trait with high genetic redundancy.
• Observed convergent phenotypic responses (fitness, metabolic rate, fat content).
• Identified 99 selected alleles contributing to adaptation, with heterogeneous frequency changes across replicates.

Conclusions:

• Drosophila simulans populations possess a large reservoir of adaptive variation.
• Rapid evolution occurs via multiple alternative genetic pathways converging on a phenotypic optimum.
• Testing strategies for natural populations need to account for genetic redundancy and diverse evolutionary pathways.