Nuove conoscenze sulla simbiosi microbica nelle mosche della frutta (Diptera, Tephritidae) e potenziali applicazioni per il controllo integrato delle specie dannose

This PhD thesis investigates the diversity, distribution, and functional significance of microbial symbioses in the fruit fly family Tephritidae, integrating evolutionary and applied perspectives. The olive fruit fly, Bactrocera oleae, and its obligate symbiont Candidatus Erwinia dacicola were analysed across Mediterranean and worldwide populations, revealing strong geographic structuring that mirrors the biogeographic history of the olive tree and highlights the long-term stability of this association. The work further extended to the Tephritini tribe, where the primary symbiont Candidatus Stammerula was detected for the first time in Australian species, expanding its known range (i.e. Europe and Hawaii) and underscoring its evolutionary role in host diversification. From an applied perspective, antimicrobial treatments targeting B. oleae symbionts were evaluated. In laboratory, direct treatments to infested olives with a Zn–Cu–citric acid biocomplex significantly reduced symbiont transmission and impaired the core gut bacterial communities. These findings indicate that the use of antimicrobial compounds could represent a valuable strategy to hinder the inheritance of symbiosis and compromise insect fitness within an integrated pest management framework. Finally, the study explored interactions between insect-specific viruses (ISVs) and the microbiota of Queensland fruit fly, Bactrocera tryoni, showing that while bacterial communities remained stable, fungal assemblages shifted in response to viral infection, revealing a novel dimension of host-microbe-virus interaction. Overall, this thesis improves our understanding of the intimate relationships between microorganisms and tephritids highlighting the central role of microbial symbioses in their evolution and potential as innovative targets for sustainable pest management.