Darwin’s Finches Face Risk Of Extinction

The finches who formed a major foundation for Darwin’s theory of evolution are on the verge of extinction. Charles Darwin used their varying beak size on different islands to illustrate his theory of natural selection. He stepped on the Galapagos islands, a volcanic archipelago in the Pacific Ocean off the coast of Ecuador, in September 1835. The five weeks that followed changed the world of science with his landmark “Theory of Evolution.”

A study published in the Journal of Applied Ecology on December 18 states that the birds’ well-being is threatened by a species of parasitic flies, Philornisdownsi, infesting their nests and eating their chicks, and that they have the potential to wipe them out within a few decades.

Researchers believe the finches are at a greater danger of disappearing because the flies have grown in numbers in recent years due to the weather conditions being more favorable to the insects than to the birds.

Speaking to the Daily Telegraph, professor Koop, who did the research as a University of Utah doctoral student, said the flies were first spotted in the islands in 1964 but it wasn’t until 1997 that they first showed up in a nest. She made the following statement.

“They are bad and they are causing a lot of the deaths of the finches.”

The study was performed on the medium ground finch, Geospizafortis, on Santa Cruz Island in the Galapagos, the second largest island in the archipelago after Isabela, where an estimated 270,000 medium ground finches live. An estimated 500,000 live throughout the Galapagos Islands. The research is based on five years of data collected by the academics documenting fly damage to finch reproduction. The mangrove finch is already facing potential extinction due to its limited population on Isabela island.

A few million years ago, one species of finch migrated to the rocky Galapagos from the mainland of Central or South America. At least 13 species of finch evolved from the single migrant ancestor. This process in which one species gives rise to multiple species that exploit different niches is called adaptive radiation.

The ancestral finch was a ground-dwelling, seed-eating finch. After speciation, the formation of new and distinct species in the course of evolution, in the Galapagos, a total of 14 species evolved, three species of ground-dwelling seed-eaters; three others living on cacti and eating seeds; one living in trees and eating seeds; and seven species of tree-dwelling insect-eaters. The birds express different traits in their beaks depending on the primary food source available on the island they inhabit—this is the trait Darwin identified as being an evolutionary modification.

A mathematical model was applied, based on five years of data to establish the impact flies could have on reproduction rates of the finches. In the three scenarios presented, they found that in the worst case the birds be extict in in 50 years. A more moderate fly infestation scenario gave the birds around a century. But University of Utah biology professor and lead author of the study, Dale Clayton, says the news isn’t all “doom and gloom.”

Clayton said that a “modest reduction in the prevalence of the fly” through human intervention would likely reduce the extinction rate. The scientists suggested several tactics, like the use of insecticides or the introduction of parasitic wasps that would lay eggs in the larvae of the fly and then eat them from the inside out, or the breeding of sterile male nest flies in which the flies are bred in captivity and males are irradiated to be made sterile to suppress the egg production. The hand-rearing of at-risk finch chicks could also help.

In the meantime, evolution continues, even between the finches and the flies. Clayton referred to it as “co-evolution,” in which parasites and hosts evolve in tandem. Alternatively, he also said the birds could evolve a defense mechanism through natural selection that would make the flies, specifically their larvae, less harmful.

When asked by Fusion what would Darwin make of all this? He said the following.

“I think he would be fascinated by the interaction,” said Clayton. “I assume he would be very interested in whether the birds can rapidly evolve defenses, which is possible. We’ve seen the evolution of defenses in some other populations. It’s just no one really knows how quickly it would occur.”

[Photo by Wolfgang Kaehler/Getty Images]