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Génétique Quantitative et Évolution - Le Moulon

 Sylvain GLÉMIN (invited by mtenaillon)

  -  14:00:00
 GQE-Le Moulon

Dynamic of mating system evolution and its genomic consequences in wheat relatives (Aegilops/Triticum)

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Vendredi 3 juillet 2020 à 14h00

Sylvain GLÉMIN

(ECOBIO, Université de Rennes 1)

invité par Maud Tenaillon

Dynamic of mating system evolution and its genomic consequences in wheat relatives (Aegilops/Triticum)

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 a reduced adaptive potential and to accumulate weakly 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 roles of demographic versus linked selection effects remain 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 presents a wide range of mating systems, from self-incompatible to highly selfing species. Phylogenomic analyses revealed a complex history with past hybridizations and pointed to a self-incompatible ancestor with several evolutions to different degrees of selfing.

We found a strong and continuous effect of mating system on patterns of polymorphism and selection efficacy. We also used recombination maps to estimate the effect of linked selection on patterns of polymorphism and try to distinguish it from demographic effects. We found a strong effect of linked selection that is amplified by selfing but our results also point to a role of the specific demography of species able to autonomous selfing. Finally, the comparison of polymorphism and divergence patterns suggested a (very) recent origin of selfing habit, hence a potentially rapid turnover of selfing species, raising the question of the underlying causes of high extinction rates in selfers.