Darwin's Finches are Evolving Again


Image credit: lightmatter/Flickr

When the Beagle reached the Galapagos Islands in 1835, Charles Darwin famously set out to survey the unique species that called the isolated archipelago home. Noticing that finches, which shared a common ancestor, had developed adaptations to thrive in different niches helped lay the foundation for his later description of the process of evolution.

Now, Darwin's finches are evolving again. This time, it's not in response to their place in the ecosystem but rather in defense against two invasive parasites that threaten their survival as a species.
The Galapagos Islands. Image credit: Wikimedia Commons

One of the parasites, Poxvirus avium, preys on the non-feathered skin of birds, creating lesions on the toes and legs, and around the bill and eyes. The lesions reduce the bird's ability to survive and can cause toes and even feet to fall off.

The other is the nest fly, or Philornis downsi, which was introduced to the islands in 1964. Fly larvae infest the finches' nests and feed on their non-feathered skin. The larvae cause serious, even fatal, damage to the birds. Young nest-bound chicks are especially vulnerable.

Dale Clayton, a biology professor at the University of Utah who is studying the finches, explained that:

Species have long histories of evolving together...this can lead to a balance. The parasites use hosts but don't drive them extinct because the hosts fight back. But if you pick up a parasite from one spot on Earth and drop it on another spot— something people are doing frequently—then the host animal may not have a chance. There are lots of invasive parasites. This is a big problem worldwide.

However, on the Galapagos, his research is showing, some species are learning to fight back. Looking at finches from two different islands, Daphne Major and Santa Cruz, Clayton and his team discovered that the birds are developing antibodies to combat the parasites.


Image credit: putneymark/Flickr

Finches on Daphne Major showed an antibody response to the pox virus nearly three times stronger than those on Santa Cruz, where the virus has not yet been introduced. On Santa Cruz Island, finches tested during nesting had a 1.7 times stronger antibody response to larvae attacks than those tested before nesting.

Clayton explained that the results show the finches "can respond to invasive parasites with which they have no history of association. The immune system has been activated." Why they have this ability—or whether the reaction is beneficial or more akin to an allergy response—is not yet known.

The research, however, has taken a significant step towards understanding and protecting the finches and, ultimately, all of the Galapagos' many threatened species.

Read more about the Galapagos Islands:
Galapagos Islands: Travel and Conservation (Slideshow)
The Beak of the Finch by Jonathan Weiner
3 Amazing, Galapagos-Only Birds Possibly Headed for Extinction
Sea Lion Massacre in Galapagos Mystifies Authorities

Tags: Animals | Birds