How can flies adapt via many interchangeable alleles?
Ten D. simulans replicates converged phenotypically under a new temperature regime, but used largely different selected alleles—evidence for genetic redundancy.
Source
Genetic redundancy fuels polygenic adaptation in Drosophila
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How can flies adapt via many interchangeable alleles?
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10 replicate populations were exposed to a new temperature regime.
We exposed 10 replicates of a Drosophila simulans population to a new temperature regime and uncovered a polygenic architecture of an adaptive trait with high genetic redundancy among beneficial alleles.
99 selected alleles with mean selection coefficient 0.059.
We observed convergent responses for several phenotypes—e.g., fitness, metabolic rate, and fat content—and a strong polygenic response (99 selected alleles; mean s = 0.059).
What they did
Used laboratory natural selection on 10 replicate Drosophila simulans populations under a new temperature regime, tracking phenotypes and allele-frequency changes for selective sweeps vs polygenic adaptation.
What they found
Convergent fitness/metabolic/fat phenotypes with a strong polygenic response (99 selected alleles; mean s = 0.059), yet each allele rose only in a subset of replicates. Redundancy/QT paradigms fit better than independent selective-sweep simulations.
The limits
What it doesn't show
Lab temperature selection is not a direct map of wild climate adaptation; molecular non-convergence does not mean phenotypes lack shared physiological mechanisms.
Key terms
- Polygenic adaptation
- Adaptation via frequency shifts at many loci rather than one large-effect sweep.
- Genetic redundancy
- Different beneficial alleles can substitute for one another across replicates.
- AFC
- Allele frequency change used to detect selected variants.
- Selective sweep
- Rapid rise of a strongly favored allele, often leaving a narrow genomic signature.
- Quantitative trait paradigm
- Many small-effect alleles push a trait toward a shared optimum.
- Laboratory natural selection
- Replicated experimental evolution under controlled selective conditions.
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Number of evolving replicates:
Common questions
How many replicates?
10 evolving D. simulans populations.
How many selected alleles flagged?
99 selected alleles (mean s = 0.059).
Did genetics converge across replicates?
No—alleles rose only in subsets of replicates despite phenotype convergence.
What paradigms fit best?
Redundancy and quantitative-trait paradigms beat independent sweep models.
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