The composition and diversity of bacteria forming the microbiome of parasitic organisms have implications for differential host pathogenicity and host–parasite co-evolutionary interactions. The microbiome of pathogens can therefore have consequences that are relevant for managing disease prevalence and impact on affected hosts. Here, we investigate the microbiome of an invasive parasitic fly Philornis downsi, recently introduced to the Galápagos Islands, where it poses extinction threat to Darwin's finches and other land birds. Larvae infest nests of Darwin's finches and consume blood and tissue of developing nestlings, and have severe mortality impacts. Using 16s rRNA sequencing data, we characterize the bacterial microbiota associated with P. downsi adults and larvae sourced from four finch host species, inhabiting two islands and representing two ecologically distinct groups. We show that larval and adult microbiomes are dominated by the phyla Proteobacteria and Firmicutes, which significantly differ between life stages in their distributions. Additionally, bacterial community structure significantly differed between larvae retrieved from strictly insectivorous warbler finches (Certhidea olivacea) and those parasitizing hosts with broader dietary preferences (ground and tree finches, Geospiza and Camarhynchus spp., respectively). Finally, we found no spatial effects on the larval microbiome, as larvae feeding on the same host (ground finches) harboured similar microbiomes across islands. Our results suggest that the microbiome of P. downsi changes during its development, according to dietary composition or nutritional needs, and is significantly affected by host-related factors during the larval stage. Unravelling the ecological significance of bacteria for this parasite will contribute to the development of novel, effective control strategies.
Bibliographical noteFunding Information:
Permission to conduct this study was granted by the Galápagos National Park Directorate (Project: PC-10-15: Control of the Invasive Parasite, Philornis downsi and its Impact on Biodiversity; Project: PC-23-16: Strategic Research into Impacts of Philornis downsi for its Darwin's finch hosts). This work was supported by funding from the Galápagos Conservancy and the International Community Foundation (with a grant awarded by The Leona M. and Harry B. Helmsley Charitable Trust) to the Charles Darwin Foundation. This is contribution number 2148 of the Charles Darwin Foundation for the Galápagos Islands. We thank I. Rozenboim and B. Perlman for their insights regarding avian anatomy and physiology.
© 2017 John Wiley & Sons Ltd
- Darwin's finches
- Galápagos Islands
- Philornis downsi
- host–parasite interactions