Variation and evolution of venom contents in the parasitoid wasps Psyttalia (Hymenoptera, Braconidae) and Leptopilina (Hymenoptera, Figitidae) : a cause of success and failure in biological control ? ; Variation et évolution de la composition du venin des guêpes parasitoïdes Psyttalia (Hymenoptera, Braconidae) et Leptopilina (Hymenoptera, Figitidae) : une cause possible d'échec et de succès en lutte biologique ?

Endoparasitoid wasps lay eggs and develop inside arthropod hosts, leading to their death. They have evolved various strategies to ensure parasitism success, notably the injection with the eggs of venom that suppresses the host immunity. Although venom composition has been characterized in a growing number of parasitoid families and recent studies suggest that parasitoid virulence can rapidly evolve, the intraspecific variation of venom and its short-Term evolvability remained to be investigated. This information is however essential for understanding the evolution of parasitoid host range and may have implications in biological control. This thesis allowed to demonstrate the occurrence of inter-Individual variability of venom and to develop a method based on the analysis of electrophoretic 1D profiles and the use of “R” functions allowing statistic comparison of protein quantities from numerous individuals. Then, to study the effect of this variability of the venom composition, experimental evolution studies were performed on Psyttalia lounsburyi and Leptopilina boulardi. Overall, the thesis evidenced that parasitoid venom composition (i) is variable at all studied biological levels (ii) changes rapidly, confirming its high evolvability, and (iii) influences key parameters of the parasitoid biology. This may have important implications in biocontrol and raises the question of the mechanisms sustaining this variability. ; Les guêpes endoparasitoïdes effectuent leur développement dans un hôte arthropode, entraînant sa mort. Parmi les stratégies assurant leur succès parasitaire, la plus commune est l’injection de venin dans l’hôte lors de l’oviposition, provoquant la suppression de l’immunité de l’hôte. Il est connu que la composition du venin est variable entre espèces et que la virulence des parasitoïdes peut évoluer rapidement. Pourtant la variation intraspécifique de la composition du venin n’a jamais été étudiée alors qu’elle est essentielle pour comprendre l’évolution de la gamme d’hôte des parasitoïdes, un ...