The evolution of selfing is accompanied by reduced efficacy of selection and purging of deleterious mutations

Arunkumar Ramesh, Rob W. Ness, Stephen I. Wright, Spencer C.H. Barrett

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


The transition from outcrossing to selfing is predicted to reduce the genome-wide efficacy of selection because of the lower effective population size (Ne) that accompanies this change in mating system. However, strongly recessive deleterious mutations exposed in the homozygous backgrounds of selfers should be under strong purifying selection. Here, we examine estimates of the distribution of fitness effects (DFE) and changes in the magnitude of effective selection coefficients (Nes) acting on mutations during the transition from outcrossing to selfing. Using forward simulations, we investigated the ability of a DFE inference approach to detect the joint influence of mating system and the dominance of deleterious mutations on selection efficacy. We investigated predictions from our simulations in the annual plant Eichhornia paniculata, in which selfing has evolved from outcrossing on multiple occasions. We used range-wide sampling to generate population genomic datasets and identified nonsynonymous and synonymous polymorphisms segregating in outcrossing and selfing populations. We found that the transition to selfing was accompanied by a change in the DFE, with a larger fraction of effectively neutral sites (Nes <1), a result consistent with the effects of reduced Ne in selfers. Moreover, an increased proportion of sites in selfers were under strong purifying selection (Nes > 100), and simulations suggest that this is due to the exposure of recessive deleterious mutations. We conclude that the transition to selfing has been accompanied by the genome-wide influences of reduced Ne and strong purifying selection against deleterious recessive mutations, an example of purging at the molecular level.
Original languageEnglish
Pages (from-to)817-829
Number of pages13
Issue number3
Early online date30 Dec 2014
Publication statusPublished - 1 Mar 2015


  • mating system
  • selection efficacy
  • Eichhornia paniculata
  • effective population size
  • dominance


Dive into the research topics of 'The evolution of selfing is accompanied by reduced efficacy of selection and purging of deleterious mutations'. Together they form a unique fingerprint.

Cite this