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Sylvain Glemin: The evolution of selfing and its genomic consequences. Insight from Aegilops and Capsella species

  • Datum: 13.10.2017
  • Uhrzeit: 10:00 - 11:00
  • Vortragender: Sylvain Glemin
  • Institut des Sciences de l’évolution, Montpellier, France Evolution Biology Centre, Uppsala, Sweden
  • Ort: MPIPZ
  • Raum: SR II
  • Gastgeber: Stefan Laurent
The evolution of selfing from outcrossing is one of the most frequent transitions in flowering plants. Although potentially ecologically successful on the short term, selfing is supposed to be an evolutionary dead-end on the long term because of its negative genetic consequences. Theory predicts that selfing increases genetic drift and genetic linkage, reducing genetic diversity and the efficacy of selection. In addition, selfing species are more prone to extinction/recolonization dynamics, which increases further genetic drift. Selfing species are thus supposed to have reduced adaptive potential and to accumulate deleterious mutations. In several species, genomic signatures of the negative effects of selfing have been found. However, the pace at which selfing impacts genome evolution and the relative role of demographic versus linked selection effects remains unclear. To address these questions we sequenced the transcriptome of two to 20 individuals for all 13 diploid species of the Aegilops/Triticum genus (wheat relatives) that present a wide range of mating systems from self-incompatible to highly selfing species. We found a strong and continuous effect of mating system on patterns of polymorphism and selection efficacy. Comparison of mating system and local recombination effects suggests that both linked selection and demography play a role. Finally, comparison of polymorphism and divergence patterns suggests a (very) recent origin of selfing habit, hence a potentially rapid turnover of selfing species. This raises the question of the underlying causes of high extinction rates in selfers. To address this second question we use the Capsella genus that comprises one outcrossing and three recent selfing species, also showing evidence of genomic degradation. Through a competition experiment we started to test a new hypothesis that posits that the deleterious effects of selfing, especially the mutation load, could depend on ecological conditions, being enhanced in a competitive environment. Our results are discussed in the context of the evolutionary dead-end theory of selfing evolution
 
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