DNA barcoding takes on the world

A mixed reception
Not everyone is jumping on the DNA barcoding bandwagon.

Many taxonomists, for example, agree that the gene chosen for differentiating animals is a relatively poor choice for distinguishing among plants and fungi, a point that barcoding supporters concede.

“You have to find a chunk of DNA that varies at the proper level to differentiate things that appear to be similar,” said Fred Hrusa, Senior Plant Taxonomist for the California Department of Food and Agriculture, in a telephone interview.

Hrusa, in fact, blasted the barcoding initiative as a “dangerous threat” to science that ignores how plant populations evolve in complex communities and may further erode support for taxonomy research through its “we know all the answers” mindset. Plants, he said, don’t have the same species barriers as animals and exchange genetic material too often for a method that samples only a handful of specimens to be of any use in distinguishing close relatives.

“DNA barcoding is an attempt to oversimplify a very complex problem,” he said, “and I really think it’s an attempt to put taxonomists out of business.”

Rob DeSalle, curator of invertebrate zoology at the American Museum of Natural History in New York, stressed that barcoding is not a replacement for taxonomy. In an e-mail, he said initially chilly relations between the two groups of scientists have warmed over the last five years as barcoding’s definition has become clearer. “Some taxonomists have found ways to hitch themselves to barcoding proposals and in this context are quite happy with the endeavor.”

As a way of identifying organisms, DeSalle said, barcoding’s main value is in its ability to centralize information and to allow any remains of an animal, plant or other organism to be identified so biodiversity can be regulated and protected (thus helping to enforce bans on exporting rare cats, elephant ivory or tropical birds, for example). In the future, he said, the technique may even help automate the naming and identification of biodiversity around the world.

Pilot projects
In the meantime, a range of collaborations have sprung up to barcode the world’s fruit flies, mosquitoes, birds, butterflies and moths, fish, hardwood trees, and endangered species. South Africa wants to use DNA barcoding to identify agriculture-damaging scale insects, Kenya wants it for safeguarding the commercial fisheries in its Rift Valley lakes, and Brazil would like a more accessible identification system to help protect its vanishing trees.

Buttressing the technique’s growing support, the Food and Drug Administration, Environmental Protection Agency, National Oceanic and Atmospheric Administration and Federal Aviation Administration all have launched pilot projects exploring DNA barcoding as a viable alternative to more traditional species identifications.

For the FAA’s pilot project, CBOL's Schindel said, the technique is being used to identify birds involved with aircraft collisions, a dangerous and costly phenomenon that has spurred officials to gather more information about the types of birds most often involved. “Can we change the habitats around airports to keep the birds out of flight paths of planes?” he said.

The FDA is using barcodes to monitor the problem of seafood mislabeling, like last year’s pufferfish-monkfish switcheroo, which sickened two people who ate fish soup before the case was solved. NOAA and the National Marine Fisheries Service are testing barcoding as a way of enforcing the Endangered Species Act with a joint pilot project in the Gulf of Maine. And the EPA’s pilot project is using DNA barcoding to identify the number and kinds of invertebrate animals living in Maryland streams as part of the agency’s water-quality monitoring activities. DNA barcoding also enabled EPA researchers to confirm the presence of the invasive quagga mussel in Lake Superior — positively identifying one specimen from among over 20,000 mussels.

Documenting biodiversity can be daunting when a country lacks the funding or infrastructure to do so on its own but bans the removal of any specimens beyond its borders. In India, which strictly controls the export of biological material, officials have announced plans for a new barcoding facility that would process samples acquired within the country. In other cases, researchers have negotiated agreements in which specimens are lent to more established foreign labs for DNA analysis in exchange for technological help that promotes self-sufficiency for the lending country. An upcoming workshop will try to set global standards to ensure that no samples are collected illegally.

Eventually, barcoding’s supporters hope, some of the remaining resistance will fade away when they demonstrate the technique’s benefits for applications such as border control and pest eradication. When, for example, should a port’s safety officers require fumigation before allowing in a ship that may harbor disease-carrying mosquitoes?

The answer, Schindel said, depends on the mosquito species — a not-so-simple calculation given the 3,000 known types. The difference, he said, “means using insecticides in large areas or not, so it has large environmental implications.”

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