Colonization changes the microbiota of the avian parasite Philornis downsi

Insects maintain a complex gut microbiota, often reconfigured at different life stages and vital for host biology. Laboratory-reared insects with limited microbiota may lack crucial host-microbe interactions present in the natural environment. Understanding the gut microbiotas of wild and laboratory-reared insects (with altered living environment and diet as perturbing factors) allows deeper insights into host-microbiota interactions. Accordingly, we tested the hypothesis that colonization leads to changes in the microbiota of Philornis downsi (Diptera: Muscidae), an invasive bird parasite in the Galapagos Islands. Our 16S rRNA gene-targeted microbiota studies on laboratory-reared and field-collected larvae and adults support this hypothesis. The microbiota composition of laboratory-reared larvae differs from that of larvae collected from infested nests. The latter are dominated by Enterobacteriaceae, Enterococcaceae and Pseudomonadaceae, while in the laboratory Wohlfahriimonadaceae, Enterobacteriaceae, Xanthomonadaceae, and Sphingobacteriaceae are dominant. The microbiota of laboratory-reared adults differs from field-collected adults in several aspects. Members of Dysgonomonadaceae and Ruminococcaceae are present only in the field but absent in the laboratory, while Leuconostocaceae is present in most laboratory-reared males yet absent in field-collected males. Moreover, the microbiotas of field-collected and laboratory-reared larvae differ significantly from that of adults. Together, our results reveal a differential microbiota composition and life stage associated transitions under laboratory and natural conditions. Future efforts will focus on the functional significance of this microbiota transition. This will help to develop efficient mass-rearing of P. downsi for sterile insect release, and ultimately, conservation of the iconic birds of the Galapagos Islands.