7,771 research outputs found
Multidimensional epistasis and the transitory advantage of sex
Identifying and quantifying the benefits of sex and recombination is a long
standing problem in evolutionary theory. In particular, contradictory claims
have been made about the existence of a benefit of recombination on high
dimensional fitness landscapes in the presence of sign epistasis. Here we
present a comparative numerical study of sexual and asexual evolutionary
dynamics of haploids on tunably rugged model landscapes under strong selection,
paying special attention to the temporal development of the evolutionary
advantage of recombination and the link between population diversity and the
rate of adaptation. We show that the adaptive advantage of recombination on
static rugged landscapes is strictly transitory. At early times, an advantage
of recombination arises through the possibility to combine individually
occurring beneficial mutations, but this effect is reversed at longer times by
the much more efficient trapping of recombining populations at local fitness
peaks. These findings are explained by means of well established results for a
setup with only two loci. In accordance with the Red Queen hypothesis the
transitory advantage can be prolonged indefinitely in fluctuating environments,
and it is maximal when the environment fluctuates on the same time scale on
which trapping at local optima typically occurs.Comment: 34 pages, 9 figures and 8 supplementary figures; revised and final
versio
Clonal interference and Muller's ratchet in spatial habitats
Competition between independently arising beneficial mutations is enhanced in
spatial populations due to the linear rather than exponential growth of clones.
Recent theoretical studies have pointed out that the resulting fitness dynamics
is analogous to a surface growth process, where new layers nucleate and spread
stochastically, leading to the build up of scale-invariant roughness. This
scenario differs qualitatively from the standard view of adaptation in that the
speed of adaptation becomes independent of population size while the fitness
variance does not. Here we exploit recent progress in the understanding of
surface growth processes to obtain precise predictions for the universal,
non-Gaussian shape of the fitness distribution for one-dimensional habitats,
which are verified by simulations. When the mutations are deleterious rather
than beneficial the problem becomes a spatial version of Muller's ratchet. In
contrast to the case of well-mixed populations, the rate of fitness decline
remains finite even in the limit of an infinite habitat, provided the ratio
between the deleterious mutation rate and the square of the
(negative) selection coefficient is sufficiently large. Using again an analogy
to surface growth models we show that the transition between the stationary and
the moving state of the ratchet is governed by directed percolation
Analytical study of the effect of recombination on evolution via DNA shuffling
We investigate a multi-locus evolutionary model which is based on the DNA
shuffling protocol widely applied in \textit{in vitro} directed evolution. This
model incorporates selection, recombination and point mutations. The simplicity
of the model allows us to obtain a full analytical treatment of both its
dynamical and equilibrium properties, for the case of an infinite population.
We also briefly discuss finite population size corrections
Dynamics of Competitive Evolution on a Smooth Landscape
We study competitive DNA sequence evolution directed by {\it in vitro}
protein binding. The steady-state dynamics of this process is well described by
a shape-preserving pulse which decelerates and eventually reaches equilibrium.
We explain this dynamical behavior within a continuum mean-field framework.
Analytical results obtained on the motion of the pulse agree with simulations.
Furthermore, finite population correction to the mean-field results are found
to be insignificant.Comment: 4 pages, 2 figures, revised, to appear in Phys. Rev. Let
Results of Evolution Supervised by Genetic Algorithms
A series of results of evolution supervised by genetic algorithms with
interest to agricultural and horticultural fields are reviewed. New obtained
original results from the use of genetic algorithms on structure-activity
relationships are reported.Comment: 6 pages, 1 Table, 2 figure
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