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Master Thesis

Importance des interactions intraguildes directes et indirectes sur la coexistence entre deux ennemis naturels de la mineuse de la tomate Tuta absoluta

Abstract : Direct and indirect interactions are key components in structuring ecosystems and their understanding provides a better comprehension of their dynamics. In biological control programs, interactions must be considered before any large scale use of new biocontrol agents. This study explored the relative importance of those two types of interactions on the coexistence of the generalist predator Macrolophus pygmaeus and the larval ectoparasitoïd Stenomesius japonicus under greenhouse conditions. Both prey upon a shared resource, the tomato pinworm Tuta absoluta, a pest recently arrived in Europe. Ecological niches are explored in laboratory to explain population dynamics mechanisms. We showed in a three-month greenhouse experiment that biological control agents coexistence was possible under two different densities of T. absoluta. The population dynamics revealed a negative reciprocal interaction between M. pygmaeus and S. japonicus, probably due to the strong resource competition between these two latter. Moreover, we showed in the laboratory that the predator is engaged in apparent intraguild predation with the parasitoid, which resulted in a high mortality in its descendance. Even so, these negative interactions didn't affect host suppression and the control was additive throughout the experience. However, we did not succeed in determining an ecological niche that would explain this successful coexistence. A partitioning of the resource along the vertical axis of the tomato plants in a laboratory experiment did not show segregation between the predator and the parasitoid. In another experience, adult S. japonicus were unable to choose between plants with or without predators and to mitigate the competition with M. pygmaeus. Therefore, we hypothesize that differences in life history traits could be an explanation of coexistence in our model.
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Master Thesis
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  • HAL Id : dumas-00738662, version 1

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Anthony Droui. Importance des interactions intraguildes directes et indirectes sur la coexistence entre deux ennemis naturels de la mineuse de la tomate Tuta absoluta. Sciences agricoles. 2012. ⟨dumas-00738662⟩

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