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Sortir de sa niche ancestrale : conséquences pour les interactions trophiques, le cas du chêne pédonculé et sessile

Abstract : Niche conservatism is defined as the conservation of the niche and its associated ecological traits over time. Thus, phylogenetically closely related species tend to occupy similar niches, including abiotic conditions but also biotic interactions. Hence, individuals surrounded by phylogenetically distantly related species could be considered as inhabitant of new niche. In this thesis we were interested in trophic interactions of host individuals inhabiting a new niche, represented by distantly related neighbours, as compared to hosts remaining in their ancestral niche. We studied oak hosts and their phytophages, the next trophic level, i.e. the oak phytophages and their natural enemies, and finally the ectomycorhizal fungi of oaks. Our results showed that phylogenetic isolation of oak hosts (i) decreases abundance and pressure of phytophages on oak hosts, (ii) decreases enemy pressure of specialized enemies on oak phytophages, (iii) increases ectomycorhizal fungi abundance and activity. Hence, our results indicate that phylogenetic isolation of oaks changes the intensity and the nature of biotic interactions all along the entire trophic chain based on oaks. Our results allow us to discuss the biotic forces that favor or impede the colonization of a new niche. Moreover, we suggest that phylogenetically isolated oaks, their phytophages and their ectomycorhizal mutualists undergo specific selective pressures that could trigger evolutionary differentiation in long term.
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  • HAL Id : tel-00793651, version 1

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Benjamin Yguel. Sortir de sa niche ancestrale : conséquences pour les interactions trophiques, le cas du chêne pédonculé et sessile. Biodiversité et Ecologie. Université Rennes 1, 2012. Français. ⟨tel-00793651⟩

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