The Properties of Adaptive Walks in Evolving Populations of Fungus

S.E. Schoustra, T. Bataillon, D.R. Gifford, R.K. Kassen

Research output: Contribution to journalArticleAcademicpeer-review

84 Citations (Scopus)

Abstract

The rarity of beneficial mutations has frustrated efforts to develop a quantitative theory of adaptation. Recent models of adaptive walks, the sequential substitution of beneficial mutations by selection, make two compelling predictions: adaptive walks should be short, and fitness increases should become exponentially smaller as successive mutations fix. We estimated the number and fitness effects of beneficial mutations in each of 118 replicate lineages of Aspergillus nidulans evolving for approximately 800 generations at two population sizes using a novel maximum likelihood framework, the results of which were confirmed experimentally using sexual crosses. We find that adaptive walks do indeed tend to be short, and fitness increases become smaller as successive mutations fix. Moreover, we show that these patterns are associated with a decreasing supply of beneficial mutations as the population adapts. We also provide empirical distributions of fitness effects among mutations fixed at each step. Our results provide a first glimpse into the properties of multiple steps in an adaptive walk in asexual populations and lend empirical support to models of adaptation involving selection towards a single optimum phenotype. In practical terms, our results suggest that the bulk of adaptation is likely to be accomplished within the first few steps
Original languageEnglish
Article numbere1000250
JournalPloS Biology
Volume7
Issue number11
DOIs
Publication statusPublished - 2009

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Fungi
mutation
Mutation
fungi
Aspergillus
Population
Maximum likelihood
Substitution reactions
Aspergillus nidulans
Population Density
population size
Phenotype
phenotype
prediction

Cite this

Schoustra, S.E. ; Bataillon, T. ; Gifford, D.R. ; Kassen, R.K. / The Properties of Adaptive Walks in Evolving Populations of Fungus. In: PloS Biology. 2009 ; Vol. 7, No. 11.
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The Properties of Adaptive Walks in Evolving Populations of Fungus. / Schoustra, S.E.; Bataillon, T.; Gifford, D.R.; Kassen, R.K.

In: PloS Biology, Vol. 7, No. 11, e1000250, 2009.

Research output: Contribution to journalArticleAcademicpeer-review

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