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Variation intra spécifique de résistance et de virulence dans un système hôte-parasitoïde : Approche intégrative de la spécificité des interactions

Abstract : Parasitoid species share an original way of life, between predation and parasitism. They are mostly insects that develop at the expense of other arthropods, generally other insects, which will die as a result of the interaction. As obligatory parasites, parasitoids have a reproductive success that totally depends on their ability to successfully infest their host. On the other hand, the host has no chance of reproducing if parasitism is successful, and its reproductive success thus depends on its ability to avoid or overcome parasitism.
The insect response against endoparasitoids mainly involve immune defences. Foreign invaders of large body size (such as a parasitoid egg) can be surrounded by a melanized, multicellular capsule, a process called “encapsulation”. The parasitoid success thus clearly depends on its ability to avoid or circumvent this host immune response. As a consequence, several adaptations aimed to avoid egg encapsulation (i.e. virulence strategies), have been selected during the evolutionary history of parasitoids.
The outcome of host – parasitoid interactions is thus basically determined by the reciprocal adaptations of interacting parasitoid and host species. However, intra specific variations of resistance and virulence, which are also of great importance for coevolutionary processes, have been totally unexplored.
The research work reported in this manuscript describes and analyzes intraspecific variations in parasitoid virulence and host resistance that explain variations in parasitism outcome in the Leptopilina boulardi - Drosophila yakuba system. Two parasitoid lines, having opposite virulence abilities against D. yakuba, have been compared for both host selection behaviour and virulence strategies. Results suggest the existence of a relationship between virulence properties and host selection behaviour in L. boulardi. Besides, they demonstrate that different virulence strategies, against different host species, can be found in a single parasitoid species. The physiological effects of parasitism on host immune processes are described and the nature of some of the virulence factors is analyzed.
In a last part, the genetic and physiological bases of resistance to L. boulardi in the host D. yakuba are considered, using two host lines respectively susceptible and resistant to this parasitoid.
Using data available in the L. boulardi - D. melanogaster model, the whole results are finally integrated in a broader model summarizing L. boulardi interactions with the two host species D. melanogaster and D. yakuba, which allows discussing the problem of host specificity in parasitoids at the physiological and molecular level.
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https://tel.archives-ouvertes.fr/tel-00101898
Contributor : Christine Besse <>
Submitted on : Thursday, September 28, 2006 - 1:45:58 PM
Last modification on : Friday, June 7, 2019 - 10:55:56 AM
Long-term archiving on: : Friday, November 25, 2016 - 12:07:03 PM

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  • HAL Id : tel-00101898, version 1

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Aurore Dubuffet. Variation intra spécifique de résistance et de virulence dans un système hôte-parasitoïde : Approche intégrative de la spécificité des interactions. Ecologie, Environnement. Université François Rabelais - Tours, 2006. Français. ⟨tel-00101898⟩

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