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Thesis started october 1st, 2013

Fund: ARED / INRA

Direction: Yannick Outreman & Jean-Christophe Simon

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Abstract :

Symbiotic associations between microorganisms and eukaryotes are ubiquitous in the living world. These microorganisms can play a crucial role in the evolution and ecology of the holder by changing their phenotype. These symbionts are most often heritable, extended phenotypes resulting from these symbiotic associations can be transmitted to subsequent generations and play a key role in the evolutionary trajectories of these species : for example, by conferring resistance to a natural enemy.

Such a symbiotic protection is present in pea aphid (Acyrtho siphonpisum) in interaction with bacteria Hamiltonelladefensa. This symbiosis confers to aphid aresistance against its main enemy’s attacks: the parasitoid wasp Aphidiuservi.Populations of this pest of leguminous are structured in biotypes (specialized populations on host plants). The distribution of protective symbiont within aphid populations is singular. Many aphids living on alfalfa harbored this symbiont while it is rare in populations of other biotypes A. pisum (pea, clover).

 My thesis’ aim is to understand distribution’s pattern of protective symbiont in natural populations of pea aphids through community ecology approaches for measuring life history traits, evolutionary biology or immunity.