Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
September 28, 2004
Prof discovers new bird species using DNA bar-coding
A University of Guelph professor has discovered four new species of North American birds using DNA bar-coding, a technique that identifies living things by genetics rather than appearance.
The findings of Guelph zoologist Paul Hebert and researchers from Rockefeller University and the Canadian Wildlife Service were published today in Public Library of Science Biology.
For the study, Hebert and his colleagues examined 260 North American bird species. They found distinct genetic markers in four existing species – solitary sandpiper, eastern meadowlark, marsh wren and warbling vireo – that indicate each of the species should be divided.
“This discovery tells us that in these cases, what had been identified for the past 100 years as one species is actually two,” Hebert said. “The fact that we found four new species in this one sample suggests that a global survey is likely to lead to the discovery of at least 500 unrecognized species of birds on the planet.”
Hebert was the first scientist to propose that a short DNA sequence from a gene found in all animals can be used to identify species. He called the system “DNA bar-coding,” analogous to how retail products are tagged in supermarkets to allow quick identification of millions of items.
“DNA bar-coding enables the rapid screening of large numbers of organisms and highlights those with novel bar codes that are likely to be new species,” Hebert said. The technique relies on analyzing a portion of a mitochondrial gene (cytochrome c oxidase I or COI), which plays a key role in cellular energy production.
In earlier studies, he showed that the COI gene was easy to isolate and that species in a broad range of animal life, from flatworms to vertebrates, have distinct COI sequences. In this most recent study, he set out to determine if DNA bar-coding could distinguish closely related species as well as very different ones. He chose birds because they are one of the largest and best-studied vertebrate groups.
“Birds are probably the easiest species for humans to identify,” Hebert said. “They’re big, they’re different colours, and they sing different songs. Yet even in that easy-to-identify group, there are hidden species.”
The researchers studied samples taken from specimens at the Royal Ontario Museum. They compared species flagged by DNA bar-coding against those already established by traditional taxonomic methods, which base identification primarily on sight. They first measured how much the COI bar codes varied within members of the same species, then compared this variation with the degree of variation among birds of different species.
All of the 260 bird species examined had a different COI sequence, but in the four “composite” species, there were deep divergences, indicating that each was actually two species.
The research established an initial set of bar codes for about 40 per cent of North American birds. “This is a landmark study in proving that DNA bar-coding can be used to identify known species and find new ones, and that the technique can be broadly applied,” Hebert said.
In a second study, which appeared in the Proceedings of the National Academy of Sciences this week, Hebert and other researchers used the same DNA bar-coding technique to show that the neotropical skipper butterfly is actually a species complex consisting of at least 10 species.
DNA bar-coding has several advantages over traditional identification methods, Hebert said. It requires only a small sample of tissue and it works for identifying organisms at different stages of their life, such as the eggs and larvae of insects. It also can help resolve problematic classifications, such as when only remnants or fragments are available – when birds fly into aircraft, for example.
Hebert and the other scientists hope to eventually establish a public reference library that includes DNA bar codes of known and newly discovered plants and animal species, as well as a public online database of DNA bar-code sequences. More information is available at the Barcoding Life web site.