Molecular analysis of ecological interactions for optimizing biocontrol of the invasive weed Sonchus

Par Mélodie Ollivier, CBGP Montpellier, SupAgro, INRA, CIRAD, IRD, Univ. Montpellier

Community ecology is a promising approach for optimizing biological control as an ecosystem service. For weeds, the characterization of ecological interaction networks associated to the target plant in its natural context allows deciphering the complexity of interactions within arthropods community; and gives precious clues on potential undesirable effects induced by perturbing the communities through the introduction of biocontrol agents. Based on this approach, several research questions are addressed: i) Are there differences in network structure between contrasted geographical areas and over time? ii) What is the diversity of herbivore community and what is the specificity of these herbivores for the target plant? iii) Are herbivores being suppressed by natural enemies? Our study targets the sowthistle, Sonchus oleraceus, that is native to Europe but invasive in Australia. The development of herbicide resistance makes it extremely difficult to manage in its invasive area. As an alternative to pesticide use, biocontrol solutions are explored via a collaborative research program between Montpellier SupAgro and CSIRO. First steps of the project focus on the molecular characterization and comparison of the ecological networks among three different climatic regions in its native range (in France). This is done using cutting-edge molecular approaches (i.e. metabarcoding through NGS) to reveal feeding and parasitic interactions. Network metrics such as species richness, vulnerability, linkage density, or connectance are computed and compared between sites to assess differences in levels of complexity among changing environments. The study will be further expanded to Australia in order to confront results between invasive and native ranges. It will contribute to enhance weed control and assess the ecological risks associated to the introductions of control agents.