DNA Bar-Coding Finds New Birds

A comprehensive project to catalogue all the birds in North America has identified what may be 15 new species.

A new approach to cataloguing biodiversity, known as DNA bar-coding, has identified more than a dozen potentially new North American bird species previously overlooked by legions of ecologists and bird-watchers. The birds, which are largely indistinguishable from previously known species by look or sound, were identified by slight variations in a tiny piece of DNA.

Scientists analyze the variation in a tiny piece of DNA to identify the species of an animal, such as the heron pictured above. A sample DNA “bar code” is pictured below the heron. Colored lines represent the DNA sequence. Credit: Biodiversity Institute of Ohio

Researchers ultimately hope to use the technique to create a database of almost all life on earth. "These findings set the groundwork to expand this initiative not just in birds but across animal life and beyond," says Mark Stoeckle, a molecular biologist at Rockefeller University in New York City, who was involved in the project.

Taxonomists typically identify species on the basis of factors such as what the organism looks like, where it is found, and how it behaves. But those methods can be slow and require expertise in a narrow field, such as tropical ants or Pacific algae. DNA bar-coding, on the other hand, provides a quick and efficient way to identify many organisms.

First conceived of five years ago by Paul Hebert, an evolutionary biologist at the University of Guelph in Ontario, DNA bar-coding focuses on a specific piece of mitochondrial DNA, genetic material that resides outside cell nuclei and mutates relatively frequently. Previous studies have shown that this piece of DNA--the bar code--varies more between species than within species. In North American birds, for example, closely related species have 18 times as much difference as two members of the same species.

For the new study, published this week in the journal Molecular Ecology Notes, Hebert, Stoeckle, and collaborators analyzed specimens from museums and samples collected by birders--a total of 643 species, about 93 percent of all bird species that breed in or regularly visit the United States and Canada. They identified 15 groups of birds that were previously assumed to be members of existing species but had significantly different bar codes. "I was surprised," says Stoeckle. "People have been looking at North American birds for a long time." They also found evidence that some species thought to be separate, including eight species of gulls, have the same genetic bar code and therefore may actually be members of the same species.