title: Reproductive assurance drives transitions to self-fertilization in experimental Caenorhabditis elegans.
abstract: BACKGROUND
  Evolutionary transitions from outcrossing between individuals to selfing are partly responsible for the great diversity of animal and plant reproduction systems. The hypothesis of 'reproductive assurance' suggests that transitions to selfing occur because selfers that are able to reproduce on their own ensure the persistence of populations in environments where mates or pollination agents are unavailable. Here we test this hypothesis by performing experimental evolution in Caenorhabditis elegans.
  
  
  RESULTS
  We show that self-compatible hermaphrodites provide reproductive assurance to a male-female population facing a novel environment where outcrossing is limiting. Invasions of hermaphrodites in male-female populations, and subsequent experimental evolution in the novel environment, led to successful transitions to selfing and adaptation. Adaptation was not due to the loss of males during transitions, as shown by evolution experiments in exclusively hermaphroditic populations and in male-hermaphrodite populations. Instead, adaptation was due to the displacement of females by hermaphrodites. Genotyping of single-nucleotide polymorphisms further indicated that the observed evolution of selfing rates was not due to selection of standing genetic diversity. Finally, numerical modelling and evolution experiments in male-female populations demonstrate that the improvement of male fitness components may diminish the opportunity for reproductive assurance.
  
  
  CONCLUSIONS
  Our findings support the hypothesis that reproductive assurance can drive the transition from outcrossing to selfing, and further suggest that the success of transitions to selfing hinges on adaptation of obligate outcrossing populations to the environment where outcrossing was once a limiting factor.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Theologidis
authors.forename: Ivo M
authors.initials: IM
authors.lastname: Chelo
authors.forename: Christine
authors.initials: C
authors.lastname: Goy
authors.forename: Henrique
authors.initials: H
authors.lastname: Teotónio
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D000818:Animals; D005075:Biological Evolution; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D018509:DNA, Helminth / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004777:Environment; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D060005:Genotyping Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D054817:Pollination; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction; D012641:Selection, Genetic; D057945:Self-Fertilization; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D018509:DNA, Helminth; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C492171:fog-2 protein, C elegans; D049452:Green Fluorescent Proteins