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Soft selective sweeps in complex demographic scenarios.

Benjamin A Wilson1, Dmitri A Petrov2, Philipp W Messer2

  • 1Department of Biology, Stanford University, Stanford, California 94305 bawilson@stanford.edu.

Genetics
|July 26, 2014
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Summary

Population bottlenecks can cause soft selective sweeps to become hard. The probability of soft sweeps depends on population size fluctuations and selection strength, highlighting the need for accurate demographic data.

Keywords:
adaptationcoalescent theorymutation

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Area of Science:

  • Evolutionary Biology
  • Population Genetics

Background:

  • Adaptation can occur via soft selective sweeps, where multiple new mutations arise and spread simultaneously.
  • Previous theory assumed constant population size, neglecting demographic impacts on soft sweeps.

Purpose of the Study:

  • To investigate how changing population sizes affect the probability of soft selective sweeps.
  • To develop a theoretical framework for soft sweeps under realistic demographic scenarios.

Main Methods:

  • Extended population genetic theory for soft selective sweeps.
  • Incorporated population size changes and bottlenecks.
  • Developed an analytical framework using an extended coalescent process.

Main Results:

  • Population bottlenecks can 'harden' soft sweeps by eliminating lineages.
  • The probability of soft sweeps depends on the harmonic or instantaneous mean of effective population size, depending on fluctuation speed.
  • Soft sweep probability becomes dependent on selection strength in fluctuating populations.

Conclusions:

  • Demographic history significantly influences the observation of soft selective sweeps.
  • Accurate demographic estimates are crucial for understanding adaptation from de novo mutations.