Abstract
Adaptation of asexual populations is driven by beneficial mutations and therefore the dynamics of this process, besides other factors, depends on the distribution of beneficial fitness effects. It is known that on uncorrelated fitness landscapes, this distribution can only be of three types: truncated, exponential and power law. We performed extensive stochastic simulations to study the adaptation dynamics on rugged fitness landscapes, and identified two quantities that can be used to distinguish the underlying distribution of beneficial fitness effects. The first quantity studied here is the fitness difference between successive mutations that spread in the population, which is found to decrease in the case of truncated distributions, remains nearly a constant for exponentially decaying distributions and increases when the fitness distribution decays as a power law. The second quantity of interest, namely, the rate of change of fitness with time also shows quantitatively different behaviour for different beneficial fitness distributions. The patterns displayed by the two aforementioned quantities are found to hold good for both low and high mutation rates. We discuss how these patterns can be exploited to determine the distribution of beneficial fitness effects in microbial experiments.
Highlights
Microbial populations have to constantly adapt in order to survive in a changing environment
For a population that is fixed in size, the number of classes in the population is expected to increase with the mutation rate
The average genetic variation, which is defined here as the average number of classes (N c) present in the population is shown in Fig 3 for all three DBFE domains
Summary
Microbial populations have to constantly adapt in order to survive in a changing environment. A bacterial population exposed to a new antibiotic must evolve in order to exist [1]. In asexual populations, this process of adaptation is driven only by rare beneficial mutations [2] which provide fitness advantage. In order to survive in a new environment, enough beneficial mutations should be available and the beneficial mutations should confer sufficient fitness advantage. Even though we have some understanding about the mutation rate of different microbial populations, the full fitness distribution is more complex and relatively little is known about it. For PLOS ONE | DOI:10.1371/journal.pone.0151795 March 18, 2016
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