Mohannad Ismail, actuellement chercheur visiteur chez Thierry Hance à l’UCL Louvain la Neuve, viendra nous exposer ses travaux de post-doctorat en biologie de l’invasion le jeudi 5 avril de 14h à 15h30 (amphi Peltier – Pôle Sciences, bâtiment des minimes).
Il s’est intéressé aux interactions tritrophiques entre une plante d’origine chinoise, invasive aux USA, deux espèces de phytophages (un puceron et un lépidoptère) et deux espèces de parasitoïdes.
Résumé de ses travaux :
Studies regarding biological invasion have mostly focused either on a single level trophic system, as between two plants, or on two trophic levels, such as the interaction between herbivores and their plant hosts. Importantly, a third trophic level, including natural enemies of the herbivore, is now being considered in order to broaden understanding of the dynamics of tri-trophic interactions.
In this study, we focused on two different species of herbivore of the plant host Chinese tallow, Triadica sebifera (L.) (Euphorbiaceae), which is native to China, but an aggressive invader in USA, and their parasitoids. The generalist aphid Toxoptera odinae (Homoptera: Aphidiidae) is parasitized by the aphid parasitoid Lysiphlebus confusus (Hymenoptera: Aphidiinae), and the specialist noctuid, Gadirtha inexacta Walker (Lepidoptera: Noctuidae) is host for a parasitoid belonging to subfamily (Cheloninae). By conducting behavioral studies and cage experiments involving the parasitoids of the two herbivores, we investigated whether there were differences in the responses of the parasitoid females according to the herbivore insect feeding type and plant origin.
Female parasitoids of both herbivores chose infected plants more readily than non-infected plants, for both native and invasive populations. Faced with only infected plants, there were differences in the responses of the two parasitoids. While the female parasitoids of the aphids did not distinguish between the two types of infected plants, the female Cheloninae parasitoids of the specialist noctuid more often chose the native rather than the invasive plants.
We concluded that the invasive plants evolve increased resistance to generalists, while resistance to absent specialists decreases. The results showed the importance of understanding all the processes involved in relative interactions among different trophic levels, in regulating communities.