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IAEA Helps Ecuador’s National Parks Better Understand Parasitic Fly Threatening Darwin’s Galápagos Finches


Paola Lahuatte conducting laboratory work with  larvae of the Philornis fly in the Charles Darwin Foundation laboratory. (Photo: L.D. Lalova/CDF)

The Galápagos Islands, the archipelago associated with Charles Darwin’s theory of natural selection and evolution, are a living symbol of endemic biodiversity. Today, however, at least 20 species of bird native to the islands—including several species of Darwin’s finches—are under threat from a parasitic fly, Philornis downsi. To protect the unique ecosystem of the islands, the IAEA’s technical cooperation department, with assistance from the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, is supporting Ecuadorian experts as they study the basic and reproductive biology of this pest species to eventually rear the fly under laboratory conditions and test methods for its control.

Declared a World Heritage Site in 1978 by UNESCO, the Galápagos Islands have enjoyed broad and sustained interest from tourists around the world, welcoming more than 225 000 visitors each year. However, the growing volume of tourists has paved the way for the Philornis downsi to settle, a non-indigenous species of fly that was accidentally introduced to the islands in the luggage of travelling in visitors.

“The rapid and accelerated invasion of the parasitic fly is putting at risk the long-term conservation of the land birds of the Galápagos Islands,” said Paola Lahuatte, the manager of the Philornis laboratory at the Charles Darwin Foundation’s Research Station in Galápagos islands. “In its larval state, the fly feeds on the blood of defenseless hatchlings, causing anemia, morphological changes to the beak (which affects feeding) and often death. Its broad host range, adaptability and the lack of natural enemies has caused parasitism to reach very high levels. This is causing substantial losses of hatchlings in bird nests, annually.”

The Galápagos Islands attract some 225 000 visitors, annually. Those tourists, in turn, unintentionally facilitated the introduction of the Philornis downsi pest. (Photo: S. Rowley/CDF)

The pest currently affects 20 species of birds in the archipelago, which are found nowhere else in the world. Already critically endangered, the mangrove finch is among the species most vulnerable to Philornis, with less than 100 mangrove finches in their natural habitat today.

Following a request from the Government of Ecuador, the IAEA organized an international expert meeting in June 2018 to explore solutions to the growing threat posed to the indigenous fauna of the Galápagos. The meeting was attended by national stakeholders, including representatives of the Galápagos National Park Directorate and the Charles Darwin Foundation, in addition to international experts and collaborating scientists. The participants agreed that a combination of specific insecticide treatments and captive breeding of the most threatened species could act as a temporary mitigation strategy, until other technologies—such as the sterile insect technique (SIT)—are developed and brought to bear against the Philornis flies in the archipelago.

A new national technical cooperation project[1] was recently launched to continue to address capacities-related needs in Ecuador, and particularly in the Galápagos. In addition to the procurement and delivery of critical equipment—including an incubator and laboratory consumables—the IAEA organized an expert mission in May 2019 to support the study and investigation of Philornis’ basic anatomy and reproductive biology, including analyses of the species’ mating systems and intersexual selection. 

Philornis downsi larvae and pupae found in a finch nest. (Photo: L.D. Lalova/CDF)

“We had a very productive week with IAEA experts and have made significant progress in understanding the reproductive biology of Philornis,” said Charlotte Causton, Principal Investigator at the Charles Darwin Foundation (CDF). “We conducted a large number of dissections to better understand the reproductive system of the flies and waded through the multitude of experiments that we have conducted over the years to determine which factors might contribute to mating success, allowing us to plan new experiments.  It was especially rewarding to be able to discuss the issues that we have been having with Philornis with people so knowledgeable about fly biology and reproductive biology.”

A Technical Cooperation Fellowship was awarded to Paola Lahuatte, a member of staff at the CDF,  who joined IAEA experts in December 2019 at the Joint FAO/IAEA Insect Pest Control Laboratory in Seibersdorf, Austria, to learn more about existing SIT technologies and to better understand the ongoing research related to tsetse and fruit flies, particularly the  mass-rearing of the flies, for the benefit of the appropriate authorities in Ecuador.

 “The sterile insect technique is a proven, high-quality tool for the control of plant pests around the world,” said Lahuatte. “The Galápagos National Park Directorate and the Charles Darwin Foundation, who are working together to find a solution for protecting land birds from the damaging parasite, are hopeful that this control option could be used in the Galápagos Islands in combination with other control tools.”

[1] ECU5023, ‘Building Capacity for Mass Rearing, Sterilization and Pilot Release of Aedes Aegypti and Philornis Downsi Males’

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