Soutenance publique de thèse de doctorat en Sciences biologiques - Valentine CHAPELLE

Adaptation and evolution with low genetic diversity: a combined field and laboratory study on DNA methylation variation in the mangrove rivulus Kryptolebias marmoratus

Jury

• Prof. Alice DENNIS (département de biologie, UNamur), President
  
• Prof. Frédéric SILVESTRE (département de biologie, UNamur), Supervisor and Secretary
  
• Prof. Caroline NIEBERDING (UCLouvain), Co-supervisor
  
• Prof. Ryan EARLEY (University Alabama)
  
• Prof. Sofia CONSUEGRA (Swansea University)
  
• Prof. Victoria SUAREZ-ULLOA (Panacea Coorperative Research)
  

Abstract

Many studies emphasized epigenetic mechanisms as a third source of phenotypic variation on a range of fitness-related phenotypic traits including animal behaviors. Investigating the origins and patterns of epigenetic variation (e.g. epimutations) under an evolutionary point of view is challenging as it required the natural (non-artificial) control of genetic variation among individuals to avoid genetic interference. An emerging valuable vertebrate model, the mangrove rivulus Kryptolebias marmoratus, presents a mix-mating reproductive strategy that allows us (1) to naturally produce isogenic lineages through self-fertilization and therefore to focus on epigenetic origins independently from underlying genetic sequence and (2) to generate genetic diversity gradient by controlling the balance between selfing and outcrossing rates and therefore to investigate how epigenetic and genetic sources interact. By using this model species, this thesis aimed to determine the role of DNA methylation in the adaptation and evolution of mangrove rivulus by investigating its variation and sources within and among populations from the wild or reared under standardized laboratory conditions. We choose individual and consistent behavioral variation (i.e. personality traits) as an endpoint to represent the capacity of DNA methylation to generate phenotypic variability. As results, DNA methylation diversity has been found to be a revealing parameter to characterize wild rivulus populations (strong epigenetic structure, and possibly population-specific epimutations sources), the environmental conditions they face (complex/natural habitats of standardized/laboratory conditions) and the evolutionary pathways they follow. Mangrove rivulus can be useful to investigate adaptive and evolutionary processes mediated by epigenetic mechanisms such as epigenetic buffering, phenotypic plasticity, bet-hedging strategy, Baldwin effect, phenotypic convergence and genetic assimilation.

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