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Drift in individual behavioral phenotype as a strategy for unpredictable worlds
Ryan T Maloney1,2, Athena Q Ye1, Sam-Keny Saint-Pre1,3
1Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.
Elife
|May 12, 2026
Summary
Phenotypic variability, or bet-hedging, can help populations survive. New research shows individual phenotype can also drift randomly over time, a process potentially aiding adaptation in fluctuating environments.
Area of Science:
- Evolutionary biology
- Animal behavior
- Genetics
Background:
- Phenotypic variability is observed in individuals, even with matched genetics and environment.
- This variability, termed bet-hedging, may enhance population survival in unpredictable environments.
- Individual phenotypes can also vary over time, a phenomenon termed drift in individual phenotype.
Purpose of the Study:
- To characterize bet-hedging and drift in individual phenotypes.
- To investigate the evolutionary significance of drift in behavioral phenotypes.
- To explore potential neural substrates controlling drift.
Main Methods:
- Utilized a continuous circling assay in *Drosophila melanogaster* to measure locomotor handedness.
- Compared drift and bet-hedging across different fly strains.
- Manipulated serotonin levels to assess effects on drift rate.
- Developed a theoretical framework to evaluate the adaptive value of drift.
Main Results:
- Locomotor handedness in flies spontaneously changes over various timescales.
- Independent, strain-specific differences in bet-hedging and drift were observed.
- Serotonin manipulation altered the rate of drift.
- Theoretical modeling and real-world environmental signals suggest drift can be adaptive.
Conclusions:
- Drift in individual phenotype is a distinct phenomenon from population-level bet-hedging.
- Drift may be adaptive for populations facing fluctuating selection pressures.
- Drift contributes to population-level variability and may play a significant role in adaptation.
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