The antifungal defences of Australian Acacia thrips

Social living exposes organisms to an increased risk of pathogen infection, a risk that is amplified in social insects due to several life history traits, including high population densities within colonies and high relatedness between individuals. To offset disease risk, social insects have developed specialized antimicrobial defences. The Australian Acacia thrips, a model lineage for the study of eusocial evolution, vary greatly in their life history traits, and thus provide an excellent model system to investigate how disease mitigation measures might vary in accordance with species-level characteristics, and across developmental stages for particular species. Previous studies have already described links between antimicrobial production and increasing social complexity in the thrips, but much of the basic biology surrounding this antimicrobial defence remains unknown. This thesis aims to increase our knowledge of antimicrobial production in the Acacia thrips by describing the source and structure of their antifungals, testing whether group-size and colony maturity affect antifungal strength, and by characterising antifungal production for different castes. The research presented here provides important basic information on how Acacia thrips defend against entomopathogenic fungi, and may be useful in future comparative analysis focusing on how these antifungal defences are tied to the evolution of sociality.