Testing the Role of Genetic Background in Parallel Evolution Using the Comparative Experimental Evolution of Antibiotic Resistance

Tom Vogwill, Mila Kojadinovic, Victoria Furió, R. Craig Maclean*

*Corresponding author for this work

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Parallel evolution is the independent evolution of the same phenotype or genotype in response to the same selection pressure. There are examples of parallel molecular evolution across divergent genetic backgrounds, suggesting that genetic background may not play an important role in determining the outcome of adaptation. Here, we measure the influence of genetic background on phenotypic and molecular adaptation by combining experimental evolution with comparative analysis. We selected for resistance to the antibiotic rifampicin in eight strains of bacteria from the genus Pseudomonas using a short term selection experiment. Adaptation occurred by 47 mutations at conserved sites in rpoB, the target of rifampicin, and due to the high diversity of possible mutations the probability of within-strain parallel evolution was low. The probability of between-strain parallel evolution was only marginally lower, because different strains substituted similar rpoB mutations. In contrast, we found that more than 30% of the phenotypic variation in the growth rate of evolved clones was attributable to among-strain differences. Parallel molecular evolution across strains resulted in divergent phenotypic evolution because rpoB mutations had different effects on growth rate in different strains. This study shows that genetic divergence between strains constrains parallel phenotypic evolution, but had little detectable impact on the molecular basis of adaptation in this system.

Original languageEnglish
Pages (from-to)3314-3323
Number of pages10
JournalMolecular Biology and Evolution
Issue number12
Early online date16 Sept 2014
Publication statusPublished - Dec 2014

Bibliographical note

The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement no. 281591 and from the Royal Society. V.F. was supported by an MEC Postdoctoral Fellowship from the Spanish Government (EX-2010-0958). T.V. and M.K. carried out the experimental work and analyzed experimental data with R.C.M.; V.F. constructed the phylogeny; V.F. and T.V. carried out comparative analyses; T.V. and R.C.M. prepared the manuscript and all authors contributed to designing the study.


  • antibiotic resistance
  • experimental evolution
  • comparative biology
  • adaptation
  • Pseudomonas
  • selection experiment


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