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Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.

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Following the Dynamics of Structural Variants in Experimentally Evolved Populations

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Predictability of evolution depends nonmonotonically on population size.

Ivan G Szendro¹, Jasper Franke, J Arjan G M de Visser

¹Institute of Theoretical Physics, University of Cologne, 50937 Cologne, Germany.

Proceedings of the National Academy of Sciences of the United States of America

|December 26, 2012

Summary

Evolutionary predictability in Aspergillus niger shows a complex pattern with population size. Repeatability initially increases then decreases due to single and double mutation rates, challenging common assumptions about deterministic evolution.

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Area of Science:

Evolutionary Biology
Computational Biology
Microbial Genetics

Background:

Understanding the balance between contingency and determinism is crucial in evolutionary research.
Evolution experiments, particularly with microbes, often monitor adaptive change repeatability to assess predictability.
Previous studies suggest larger populations might lead to more deterministic evolutionary outcomes.

Purpose of the Study:

To computationally investigate evolutionary predictability using a detailed fitness landscape.
To quantify the repeatability of adaptive mutations in Aspergillus niger across varying population sizes.
To explore the influence of mutation supply rates on evolutionary predictability.

Main Methods:

Utilized an experimentally determined eight-locus fitness landscape for Aspergillus niger.
Employed computational simulations to model evolutionary trajectories and endpoints.
Defined and analyzed entropy measures to quantify evolutionary predictability and mutational pathways.

Main Results:

Evolutionary predictability exhibited a non-monotonic relationship with population size (N).
Predictability initially decreased and then increased with N, influenced by single (Nμ) and double (Nμ²) mutation supply rates.
The mutation rate (μ) significantly modulated the amplitude of this predictability pattern.

Conclusions:

The study challenges the notion of increasingly deterministic evolution in large populations.
Evolutionary predictability is shaped by a complex interplay between population size and mutation dynamics.
Findings are generalizable across different fitness landscapes, highlighting the robustness of observed patterns.