SMILE

Stochastic Models for the Inference of Life Evolution

Properties of selected mutations and genotypic landscapes under Fisher’s Geometric Model

Blanquart, F., Achaz, G., Bataillon, T., Tenaillon, O.

Evolution; international journal of organic evolution

2014

The fitness landscape – the mapping between genotypes and fitness – determines properties of the process of adaptation. Several small genotypic fitness landscapes have recently been built by selecting a handful of beneficial mutations and measuring fitness of all combinations of these mutations. Here we generate several testable predictions for the properties of these small genotypic landscapes under Fisher’s geometric model of adaptation. When the ancestral strain is far from the fitness optimum, we analytically compute the fitness effect of selected mutations and their epistatic interactions. Epistasis may be negative or positive on average depending on the distance of the ancestral genotype to the optimum and whether mutations were independently selected, or co-selected in an adaptive walk. Simulations show that genotypic landscapes built from Fisher’s model are very close to an additive landscape when the ancestral strain is far from the optimum. However, when it is close to the optimum, a large diversity of landscape with substantial roughness and sign epistasis emerged. Strikingly, small genotypic landscapes built from several replicate adaptive walks on the same underlying landscape were highly variable, suggesting that several realizations of small genotypic landscapes are needed to gain information about the underlying architecture of the fitness landscape.

Bibtex

@article{blanquart_properties_2014,
Author = {Blanquart, François and Achaz, Guillaume and
Bataillon, Thomas and Tenaillon, Olivier},
Title = {Properties of selected mutations and genotypic
landscapes under {Fisher}’s {Geometric} {Model}},
Journal = {Evolution; international journal of organic evolution},
Volume = {68},
Number = {12},
Pages = {3537--3554},
abstract = {The fitness landscape – the mapping between
genotypes and fitness – determines properties of the
process of adaptation. Several small genotypic fitness
landscapes have recently been built by selecting a
handful of beneficial mutations and measuring fitness
of all combinations of these mutations. Here we
generate several testable predictions for the
properties of these small genotypic landscapes under
Fisher’s geometric model of adaptation. When the
ancestral strain is far from the fitness optimum, we
analytically compute the fitness effect of selected
mutations and their epistatic interactions. Epistasis
may be negative or positive on average depending on the
distance of the ancestral genotype to the optimum and
whether mutations were independently selected, or
co-selected in an adaptive walk. Simulations show that
genotypic landscapes built from Fisher’s model are
very close to an additive landscape when the ancestral
strain is far from the optimum. However, when it is
close to the optimum, a large diversity of landscape
with substantial roughness and sign epistasis emerged.
Strikingly, small genotypic landscapes built from
several replicate adaptive walks on the same underlying
landscape were highly variable, suggesting that several
realizations of small genotypic landscapes are needed
to gain information about the underlying architecture
of the fitness landscape.},
doi = {10.1111/evo.12545},
issn = {0014-3820},
month = dec,
pmcid = {PMC4326662},
pmid = {25311558},
url = {http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326662/},
urldate = {2015-04-13},
year = 2014
}

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