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Genetic Drift

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Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.

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Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.

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Robustness and predictability of evolution in bottlenecked populations.

Osmar Freitas¹, Lindi M Wahl², Paulo R A Campos¹

¹Evolutionary Dynamics Lab, Physics Department, Federal University of Pernambuco, Recife-PE, 50670-901, Brazil.

Physical Review. E

|May 19, 2021

Summary

Population bottlenecks do not significantly hinder adaptation or evolutionary predictability. Even with size reductions, evolutionary trajectories remain robust, especially when bottleneck size exceeds a few thousand individuals.

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Area of Science:

Evolutionary biology
Population genetics

Background:

Natural populations adapt through deterministic and stochastic evolutionary processes, influenced by population size.
Population size dynamics, including growth and bottlenecks, create fluctuating environments where these processes shift in dominance.

Purpose of the Study:

To investigate the impact of population bottlenecks on the process of adaptation.
To analyze how bottlenecks affect the predictability and distribution of evolutionary pathways at the genotype level.

Main Methods:

Analysis of adaptive trajectories in populations experiencing regular bottlenecks.
Genotype-level analyses to assess evolutionary pathway predictability.
Examination of fitness variance and genetic diversity under bottleneck conditions.

Main Results:

Adaptive trajectories, fitness variance, and genetic diversity become relatively insensitive to bottleneck timing when bottleneck size exceeds a few thousand individuals.
Predictability of evolutionary pathways increases with population size, irrespective of bottleneck timing.
Predictability of adaptive pathways is enhanced in more rugged fitness landscapes.

Conclusions:

Population bottlenecks have a relatively minor impact on adaptation rate and evolutionary trajectory predictability.
The timing of population bottlenecks is less critical than bottleneck size for adaptation dynamics.
Evolutionary predictability is influenced by population size and fitness landscape ruggedness.