DNA Bar-Coding Could Rewrite Book of Life
BROOKLIN, Canada, 19 Feb
Fifteen new species of birds have been discovered in North America following the first ever genetic analysis of nearly all 690 known species. A similar DNA profiling or "bar-coding" of Guyana's 87 bat species revealed an additional six genetically distinct bats.
These new species are nearly indistinguishable to human eyes and ears from known species but the analysis shows their DNA evolved along different paths millions of years previously, according research published Sunday in British journal Molecular Ecology Notes.
"DNA bar-coding will transform efforts to protect and conserve the world's biodiversity," said Paul Herbert of the Biodiversity Institute of Ontario at Canada's University of Guelph.
"You can't protect it if you can't identify it," Herbert told IPS.
The habitat of a North American shorebird called the Solitary Sandpiper is under tremendous pressure from land development and climate change. It was not previously known to have two distinct forms, yet their DNA reveals that two genetically different groups diverged about 2.5 million years ago.
"How can you develop strategies to preserve highly different genetic entities if you don't know they're there? Our work is providing the first molecular evidence of some of these splits," Herbert said.
Protecting and conserving biological diversity is important because living organisms play central roles in all ecosystems that provide services like clean air and water that all life, including humans, depends on. And it is the diversity of interacting species that is the key to the health and resilience of ecosystems.
Using DNA to identify species is not new but what Herbert and colleagues have developed is a way of standardising the genetic analysis so that it can be done quickly and at low cost.
"Three hours and five dollars in chemicals" is all it now takes to identify the species from a tissue or feather sample, he said.
DNA is found in all living things and is a complex molecule that contains all the genetic instructions for an organism to develop. Not surprisingly, the DNA of a human is different and more complex than that of a worm -- although mouse DNA is similar to human DNA. The genetic differences within the millions of pieces that make up DNA among animal species were very hard to find.
After 20 years of searching and several years of testing, sampling and other field research, Herbert's breakthrough was the discovery of a portion of a gene called cytochrome c oxidase I (COI). COI appears to be biology's unique bar code for all animal species.
Port inspectors and wildlife officials will be able to quickly obtain genetic identification of a shipment of animal skins or fish filets to determine if they come from illegal or endangered species, Herbert says.
Airport officials can identify the remains of birds that are swallowed, sometimes disastrously by the jet engines of airplanes. Many thousands such "bird strikes" occur annually and by identifying the species most often running afoul of the engines, officials can prevent them from nesting near airports.
The technology is being used to set the boundaries for national parks in Madagascar and to learn more about the impacts of development pressure in the Amazon rainforest.
Among the many applications, none may be more controversial than telling the birding world, including ornithological experts, that there are 15 new species of birds in the U.S. and Canada.
"These are 15 overlooked species -- genetically distinct but look[ing] the same," said Mark Stoeckle of Rockefeller University in New York City and a co-author of the paper in Molecular Ecology Notes.
Considering how well studied North American birds are, that result came as a surprise, Stoeckle told IPS.
"Can we use DNA alone to define a species? Perhaps in future, but right now we need expert opinion," he said.
Some of those experts have argued previously that this technology remains unproven. Species identification and classification is called taxonomy, and it has a rich scientific tradition of more than three hundred years.
However, the new genetic analysis shows "there are a number of cases of deep genetic divergences within what are currently called single species," Herbert said.
Even though birds may appear very similar to human observers, a species with a distinct DNA barcode very rarely interbreeds; they literally find birds of a feather as mates. Also, the fauna (birds and bats) newly distinguished by virtue of unique DNA do not yet have unique names. That issue and process is the subject of scientific discussion and debate.
"We would raise hackles if we said DNA is now the only way to ID species," Herbert noted.
Taxonomy, however, is difficult, tedious and painstaking work and takes many years to develop expertise.
For example, Stoeckle discovered an unusual centipede while wandering in New York's Central Park one day. It took four years of work by centipede experts, who happen to be in Italy, to identify it as a new species after visually comparing it to all other identified centipedes.
DNA bar-coding will make this happen much more quickly, he said.
More importantly, the technology means that nearly all living things on the planet could be actually identified. Right now not even all of the world's 5,500 mammals have been identified. Biologists estimate that there might be two million species on earth, not including bacteria and fungi.
Herbert says that in just seven years, they could build a DNA bar code "library" that would precisely identify 500,000 animal species -- including insects, invertebrates and fish. The cost would be a relatively modest 100 million dollars for the Bar Code of Life Data Systems and fundraising efforts are underway around the globe. Already the Bar Code of Life has catalogued more than 25,000 species.
"What it will mean effectively is that researchers will find a barcode linked to just about anything encountered anywhere on the planet," Herbert said.
And by then biologists in the field will have a hand-held device, akin to a GPS, that will tell them precisely what species any hair or feather or insect shell found along a remote jungle trail belongs to.
"Our job is to reveal how many species there are on the planet and provide really simple tools to tell one species from another," Herbert concluded.