How a Galpagos bird lost the ability to fly – Bend Bulletin


The birds of the Galpagos Islands are playing a role in understanding evolution.

When Charles Darwin visited the islands, it was the variety of finch beaks that helped him understand how one species could evolve into many.

The Galpagos cormorants, the only species of cormorant to have lost the ability to fly, have enabled scientists to pin down the genes that led to this species split from other cormorants 2 million years ago.

They are genes that are present in birds, mammals and most animals, including the worm often studied in laboratories: C. elegans. In fact, they are even present in some algae. Their ultimate effect varies, however. In humans and in the cormorants, the genes affect bone growth. But mutations in humans can cause dreadful diseases; in the birds, they caused smaller wings, which were not effective for flight, and a weaker breastbone.

Alejandro Burga, who analyzed the DNA of these and other cormorants with his colleagues, is a researcher in the lab of Leonid Kruglyak, the chairman of human genetics at UCLAs medical school. He said he and Kruglyak were discussing how they might use the increasing power of modern genetics to investigate how new species develop.

On a trip to the Galpagos, Kruglyak viewed cormorants as an ideal subject, partly because of their relatively recent evolution as a species and their obvious difference from all their kin.

Patricia Parker, a behavioral ecologist at the University of Missouri, St. Louis, who studies bird diseases in the Galpagos, provided tissue samples for DNA of the flightless cormorants. She had in her freezer over 200 samples of this bird, Burga said.

He and other researchers found that a gene called Cux1 and some others were involved in the growth of cilia. These whiplike structures on the surface of cells can function in movement in single-celled animals. But in birds and humans, they work like antennas, and one of their jobs is to pick up biochemical signals for bone growth.

The end result of mutations in Cux1 in humans can be terrible diseases, called ciliopathies. In the cormorants, however, the result seems to have been to prematurely stop bone growth in the wings, resulting in the loss of flight, but leaving the birds to thrive in the water and on land.

Without a knowledge of DNA and the tools of modern genomics, Darwin could not have come up with the conclusions of the current study, published in Science.

But he certainly would have had something to say.



How a Galpagos bird lost the ability to fly - Bend Bulletin

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