Darwin’s finches face a deadly new invader as the parasitic avian vampire fly spreads across 15 islands of the Galápagos archipelago, according to research published on October 30, 2026, in the journal Molecular Ecology.
The larvae of the avian vampire fly (Philornis downsi) feed on the blood and tissue of developing chicks. They often kill 100 per cent of the brood. Ever since they were first located in bird nests back in 1997, these insects have evolved into a premier danger against the continued existence of Darwin’s finches.
New Macquarie University-led research uses genomic evidence to uncover how the parasite spreads between islands. This provides vital information for efforts to control its impact across the archipelago. The parasitic insect preys upon multiple varieties of those same finches that famously assisted naturalist Charles Darwin in figuring out the mechanisms behind species evolution and environmental adaptation.
PhD student Abbie Hay and Associate Professor Rachael Dudaniec from Macquarie’s School of Natural Sciences analysed flies collected from five major Galápagos islands and from mainland Ecuador. By sequencing and comparing the genomes of flies collected from different islands, the researchers traced patterns of directional movement and genetic diversity. The study reveals genetic migration pathways of the vampire fly across the Galápagos archipelago.
The findings revealed genetic divergence between mainland and Galápagos vampire fly populations. Researchers identified the island of San Cristóbal as a likely point of entry and source population. San Cristóbal is the closest island to the Ecuadorian mainland and historically the first docking point for cargo vessels.
“Our results suggest that the fly may be travelling from the mainland to San Cristóbal with human assistance, and from there to other islands through a combination of human activity and natural dispersal,” Dudaniec told The Lighthouse.
Island species are particularly susceptible to invasive parasites and pathogens. Having evolved in relative isolation, many lack the defences needed to withstand newly introduced threats.
“By identifying which populations are genetically connected, we can better understand where flies may be coming from and where control efforts could have the greatest impact,” Dudaniec told The Lighthouse.
Drawing upon a foundation of over twenty years of scientific investigation into the dynamic between Darwin’s finches and the avian vampire fly, this project expands our knowledge base. This work was led by Professor Sonia Kleindorfer, now based at the University of Vienna.
“Our findings are critical for prioritising islands for control strategies that will reduce the impact of the vampire fly on the finches and other vulnerable endemic birds,” Dudaniec told The Lighthouse.
Looking outward past the Galápagos archipelago, these discoveries emphasize how powerful genomic tools can be for monitoring biological invasions and shaping effective conservation policies in fragile island habitats.
