Subject: [SciPol 483] Understanding the Evolutionary Fate of Finite Populations: The Dynamics of Mutational Effects

From: "MsRedSonya" <[email-masked]>
Date: Thu, 05 Apr 2007 06:31:24 -0000

Understanding the Evolutionary Fate of Finite Populations:
The Dynamics of Mutational Effects
http://dx.doi.org/10.1371/journal.pbio.0050094

PLoS Biology 5 (4),
94 (2007)

info:doi/10.1371/journal.pbio.0050094

..."In any population, two factors
determine whether the average fitness of individuals will increase
(adaptation)
or decrease: the size of the population and the distribution of
mutational
effects (i.e., the relative rates and effect sizes of beneficial and
deleterious
mutations). Although it is relatively simple to get quantitative
information on
population size, it is much harder to gain insight into the
distribution of
mutational effects. Very little information exists on the relative
rates of
beneficial versus deleterious effects, on the shapes of mutational
distributions, or on whether the distributions change over time. Thus,
it
remains difficult to even speculate whether a given population will
adapt over
time. Here, we use laboratory evolution of a bacterial virus to
quantify the
distribution of mutational effects. Our results reveal that the
average impact
of a mutation is approximately constant with respect to fitness, that
most
mutations have small effects, and that the rate of beneficial mutation
depends
on the fitness of the organism. Our study demonstrates the simple, but
perhaps
underappreciated fact that mutational effects are dynamic. It also
proposes and
tests an explicit model of adaptation in which organismal fitness
specifies both
the rate and distribution of deleterious and beneficial mutations, and
it
presents specific and testable predictions of the circumstances under
which
populations will adapt. "...

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