The role of microbial symbionts in the niche shift of Drososphila suzukii

Insects are associated with microbes that have demonstrable effects on the insect metabolism and performance. For pest insects, it is especially important to understand these associations, as these can be causal to their pest status, and it can provide targets for pest management approaches. The insect-microbe associations are often vital for the fitness of the host. Drosophila suzukii, an invasive pest, attacks a variety of unripe fruits, unlike the other members of Drosophilidae, which feed on rotten fruits.

What is the role of microbial symbionts of D. suzukii for its niche shift from rotting to fresh ripening fruits, and its ability to feed on a wide variety of fruits? Importantly, larvae of Drosophila critically depend on yeasts and other microorganisms for the uptake of essential nutrients for body-tissue construction. The abundance and composition of microbial communities differ vastly in the new niche to which D. suzukii adapted. I want to examine the role of bacterial symbionts and yeasts on D. suzukii development, fitness and behaviour. The metabolism, longevity and pheromone production of the sibling species D. melanogaster have all been shown to depend on microbiome composition predicting a similar function of the microbiome in D. suzukii.

I hypothesize that the ecological niche shift and the polyphagous nature of D. suzukii is due to its associations with microbial symbionts. I will first examine the diversity, the co-occurrence patterns and infection rates of the associated microbes of D. suzukii in a range of fruits. I will further dissect the functional roles of microbial symbionts on their hosts' development and behaviour. Additionally, I will study their effect on chemical communication by analysing how the pheromones of D. suzukii are influenced by their symbionts. This will reveal whether and how microbes may have contributed to the ecological niche shift of this invasive pest species.