Bacterial communities of the twisted-wing endoparasitoid Dipterophagus daci (Strepsiptera) are less diverse than of its host and dominated by Wolbachia

Bacterial communities in insects can play vital roles in insect fitness and health, and are influenced by abiotic and biotic factors, including the interactions between hosts and endoparasitoids. While many studies have investigated the microbiome of free-living insects, the microbiomes of endoparasitoids and their interactions with parasitised hosts are less known. Due to their constrained host environment, endoparasitoids are expected to have simpler yet distinctive microbiomes relative to that of their hosts. Here, we used high-throughput 16S rRNA gene amplicon sequencing to characterise the microbiomes of the strepsipteran endoparasitoid Dipterophagus daci and seven of its tephritid fruit fly host species. In comparison to the fruit fly hosts, the bacterial communities of D. daci were less diverse and contained far fewer taxa. The communities were dominated by Proteobacteria (> 96%), mainly attributed to the overbearing presence of Wolbachia, with very minor other bacterial community members indicative of an overall simpler microbiome in D. daci than its host fruit flies. In contrast, a dominance of Wolbachia was observed neither in fruit flies parasitised by concealed early stages of D. daci nor unparasitised fruit flies. Our results, however, indicated that early stages of D. daci parasitisation resulted in changes in the bacterial community structure in parasitised flies. Additionally, parasitisation with early stages of Wolbachia-positive D. daci was associated with a change in the relative abundance of some bacterial taxa when compared with parasitisation with early stages of Wolbachia-negative D. daci. Besides being the first characterisation of bacterial communities in a strepsipteran, our study provides insights into the effect of early stages of parasitisation on bacterial communities in the host, and therefore contributes to the understanding of host-endoparasitoid interactions. Furthermore, our study provides further evidence that D. daci is the true host of Wolbachia previously detected in tephritid fruit flies parasitised by concealed early stages of this endoparasitoid.