November 19, 2009
Charles Darwin’s Findings Hold Key To Saving Rare Bird
Two birds collected by Charles Darwin back in 1835 could help bring back a rare mockingbird to the Galapagos Islands.
The DNA was taken from the specimens by a team of geneticists and then compared to DNA from living sub-populations on two other islands. The researchers discovered genetic hints on the best way to conserve the birds.
Darwin and Robert Fitzroy, the captain of HMS Beagle, collected samples from Floreana Island during their trip to the Galapagos more than 170 years ago.
Shortly after his famed expedition, human impact on its delicate habitat led to the extinction of the Floreana mockingbird (Mimus trifasciatus) on that particular island.
There are now only two small sub-populations surviving on two tiny satellite islets, Champion and Gardner-by-Floreana.
According to researcher Karen James from the Natural History Museum of London, the Floreana mockingbird was one of the rarest birds in the world.
"It was also important for Darwin's realization that organisms might evolve independently on islands," she told BBC News.
The Charles Darwin Foundation, which conducts conservation research in the Galapagos, is working with Durrell Wildlife Conservation Trust to reintroduce the birds to Floreana.
Dr. James noted that in order for the reintroduction to be successful, the restored population must be "as close as possible to what existed before".
The researchers have to study the Floreana birds extensively to see what this population would look like.
"There are very few of these specimens," Dr James explained. "But the Natural History Museum has two of them and they just so happened to have been collected by Darwin and Fitzroy."
The team had the unique opportunity to take tiny samples form the toe pads of each historic specimen, in order to extract DNA.
They found "genetic signals" in each of the two surviving species that were also found in Darwin's samples, which means that the two sub-populations split from each other very recently. The researchers believe that it was this split that led to the extinction of the Floreana mockingbird. This extinction would have burned the "bridge" between the two populations, making it impossible for them to interbreed.
Though they have evolved independently and become inbred, this study revealed that the tiny sub-populations have kept much of the key "genetic variation" once present in the mockingbirds on Floreana.
This bodes well for the survival of the species, and has led the researchers to conclude that future conservation plans should focus on protecting "the two satellite populations in situ and establishing a single third population on Floreana".
In order to maximize "genetic diversity", the reintroduction could bring birds from both islands, the researchers said.
Dr. James said the project emphasizes the importance of historic specimens.
"Though Darwin knew nothing of DNA, the specimens he and Fitzroy collected have, after 170 years of safe-keeping in collections, yielded genetic clues to suggest a path for conservation of this critically endangered and historically important species," she said.
On the Net:
- Biology Letters
- University of Zurich
- Natural History Museum of London
- Charles Darwin Foundation
- Durrell Wildlife Conservation Trust