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Évolution et mécanismes d’évitement de la consanguinité chez un hyménoptère parasitoïde Venturia canescens

Marie Collet 1
1 Evolution, adaptation et comportement
Département écologie évolutive [LBBE]
Abstract : Inbreeding is well known by biologists to lower the fitness of individuals by or example decreasing survival or fertility. Therefore, natural selection should favour behaviours preventing the reproduction of genetically-related individuals or mitigating harmful consequences, called inbreeding depression. Inbreeding depression is particularly visible in Hymenoptera with a sex-determination system called single-locus Complementary Sex Determination (sl-CSD), where it leads to the production of diploid males that are either unviable or sterile. My PhD work has thus been devoted to the study of sib-mating avoidance in natural populations of a parasitoid with sl-CSD, Venturia canescens, and to understand the cues used by females recognize their kin. We first studied the link between habitat type (continental, island or captive), genetic diversity and diploid male production in 11 V. canescens populations. Indeed, a theoretical framework called "Diploid male extinction vortex" predict a negative correlation between populations’ isolation, genetic diversity and diploid male production that could lead to the extinction of hymenopteran populations.We actually showed a negative correlation between genetic diversity and diploid male production in isolated populations. Previous studies have furthermore demonstrated kin discrimination and sib-mating avoidance by V. canescens females in the laboratory. We therefore studied the sibmating avoidance behaviour in natural populations of this species by genotyping more than 450 wild individuals and their offsprings. We demonstrated that females tolerated inbreeding in the wild as well as in the laboratory when several males were present. We highlighted the importance of environmental conditions on mate choice. At last, we were interested in the kin recognition system and researched the chemical cues used by females in two ecological contexts, mate choice and superparasitism avoidance. This allowed us to identify similarities in the composition of the two chemical signals and that they were not interchangeable between the two studied ecological contexts. In the end, the results we obtained shed new light on the necessary conditions for the apparition of sib-mating avoidance in natural populations, as well as on the cues used for kin recognition in a parasitoid
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Submitted on : Tuesday, January 30, 2018 - 10:25:08 AM
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Marie Collet. Évolution et mécanismes d’évitement de la consanguinité chez un hyménoptère parasitoïde Venturia canescens. Evolution [q-bio.PE]. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSE1338⟩. ⟨tel-01696129⟩

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