New bird, bat species revealed by extensive DNA barcode studies
Scientists complete DNA portrait of US, Canadian Bird Species, Guyanese
Public release date: 18-Feb-2007
At unprecedented levels of difficulty involving highly biodiverse and
continent-sized landscapes, scientists have successfully tested their
ability to identify and DNA "barcode" entire assemblages of species --
the prelude to a genetic portrait of all animal life on Earth.
Revealing their results in the UK journal Molecular Ecology Notes, they
report having assembled a genetic portrait of birdlife in the U.S. and
Canada, and announce the startling discovery of 15 new genetically
distinct species, nearly indistinguishable to human eyes and ears and
consequently overlooked in centuries of bird studies.
The barcoders also successfully logged the DNA attributes of 87 bat
species of Guyana and reveal six new species, characterized by unique
genetic make-up. One of the new species, a look-alike of Trachops
cirrhosus, feasts on frogs.
As well, the scientists report that 14 pairs of North American bird
species with separate identities are in fact DNA twins, two trios of
bird species are DNA triplets, and no less than eight gull species are
virtually DNA identical.
The complementary papers describing the bird and bat initiatives were
authored by researchers from Guelph, Ottawa and Toronto, Canada, and
from New York City and Washington D.C., USA.
The bird researchers obtained DNA from "voucher" specimens in museums,
augmented by samples sent in by scores of people. In all, more than
2,500 specimens were barcoded.
The DNA portrait of 643 bird species, from the Arctic tundra to the
temperate woodlands to the Florida Keys, represents 93 percent of 690
known breeding species in the U.S. and Canada. Work continues to
collect DNA of the remaining 47 listed North American species, as well
as several more considered extinct, specimens of which exist in museums.
The work builds on 2004 research which involved only 260 bird species,
criticized at the time as too narrow geographically and taxonomically
to prove that bird species can be reliably distinguished through DNA.
"Now with the vast majority -- 93 to 94 percent -- of birds on the
continent barcoded it's hard to argue that barcoding might work for the
easy stuff but miss the difficult cases of closely related taxa," says
Dr. Paul Hebert of the Biodiversity Institute of Ontario, Guelph
University, Canada, who co-authored both the bird and bat papers.
"People have watched birds for so long we might think every different
tweet has been heard, every different color form observed," says Dr.
Hebert. However, "there are a number of cases of deep genetic
divergences within what are currently called single species," he says.
The "cryptic species" are those with unique DNA barcodes but
differences of song and plummage so subtle as to make them virtually
indistinguishable from some other species. They are typically "small
brown ground-dwelling shrubbery birds that don't attract a lot of human
Unique DNA barcodes for provisional new bat species were obtained from
look-alike specimens of several bats, including Trachops cirrhosus,
which feasts on frogs.
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
"Did we find concordance between barcode results and conventional
taxonomy? The answer is, resoundingly, yes. In 95 percent of cases,
entities recognized as species are barcode distinct," adds Dr. Hebert.
People who put tiny bands on birds to help track migrations contributed
samples for the study. Banders are extremely good at identifying
species "but even they can't always identify a bird in the hand," says
Dr. Hebert. "In such cases, they appreciate having a barcode record to
identify with certainty the bird they banded."
Dr. Stoeckle of Rockefeller University says the world recognizes about
10,000 bird species today and predicts that, at a global scale, DNA
barcoding will distinguish at least 1,000 potential new species. The
researchers hope to complete an all-bird DNA inventory by 2011.
Given the continent's legions of bird specialists, he says he was
surprised by the extent of "hidden diversity" revealed in North
America, and by the clear DNA distinctions between species.
Dr. Stoeckle cautions that "some pairs of listed species now shown to
be DNA twins may be relatively young species and prove different over
time." As well, he notes, there is no universal scientific agreement on
what defines a species.
"Wouldn't you think we'd have all of the world's 5,500 mammals
identified by now? The scientific community has been at it for 250
years," says Dr. Hebert. Roughly 1,100 or 20 percent of the world's
5,500 mammals are bats.
Adding six new bat species to the 87 surveyed from Guyana is a
surprisingly high percentage, he notes. In all, some 840 bat specimens
"We wanted to give barcoding the toughest test possible. The bats of
Guyana have been the subject of intensive taxonomic work and yet we
found we could recognize 100 percent of the surveyed species and
discovered a number of overlooked bats."
Stray hairs could tell the kind of bats in your belfry -- or which bats
are bumping into wind turbines, whose blades whack thousands of the
animals each year, he added.
Barcodes Important to Commerce, Security and Conservation
Barcoding can identify a species from bits and pieces. When fully
established, the barcode database will help quickly identify
undesirable animal or plant material in food and detect regulated
species in the marketplace.
Barcoding will help reconstruct food cycles by identifying fragments in
stomachs and assist plant science by identifying roots sampled from
soil layers. A standardized library of barcodes will enable more people
to identify species -- whether abundant or rare, native or invasive --
engendering appreciation of biodiversity locally and globally.
The importance of this work to conservation is particularly critical,
adds Dr. Hebert. The Solitary Sandpiper shorebird, its habitat
increasingly under pressure from land development and climate change,
was not known previously to have two forms, yet their DNA reveals two
distinct groups split 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."
The work with birds and bats also helps aviation and is supported in
part by the U.S. Federal Aviation Authority and U.S. Air Force.
According to Carla Dove of the Smithsonian Institution: "Knowing which
birds are most often struck, and the timing, altitude and routes of
their migrations, could avert some of the thousands of annual
collisions between birds and aircraft, military and civilian."
In a few years, field researchers, indeed many interested citizens,
could employ hand-held DNA devices for nearly instant species
identification. Says Dr. Hebert: "For cases where it is not convenient
to identify species based on shape, sound and color, even non-experts
could identify them based on DNA strings."
Once miniaturized, the many potential uses of quick DNA barcoding
embrace food and agriculture, forestry and security, including
certification of species for market, controlling pest animals and
preventing invasions of species via international trade. A DNA barcoder
could name the vegetables in your soup.
Perhaps the biggest surprise is that DNA barcoding works as well as it
does, that a relatively short code of genes distinguishes species so
clearly and there isn't more blurring between species, says Dr.
Barcoding has prompted speculation and theories about mechanisms that
strip variation out of species and keep them sharply distinct --
periodic "selective sweeps" -- and the reasons behind them.
"This work is raising questions about how evolution works and what
species are," he says.
So far, the Barcode of Life Data Systems (www.barcodinglife.org) has
catalogued more than 25,000 species of all types, and over 200,000
individual records; both numbers more than doubled in the past year.
Whenever possible, museum specimens have been used to create the DNA
barcode reference library, enabling scientists to re-check and verify
any puzzling results.
The Smithsonian has barcoded an Ivory-billed woodpecker preserved from
decades ago, "so if birdwatchers now find a fresh feather, we could
strongly confirm the bird still survives," says Dr. Hebert.
The researchers are looking to raise US $100 million to create 10
million records of 500,000 animal species by 2014.
Says Dr. Hebert: "What it will mean effectively is that researchers
will find a barcode linked to just about anything encountered anywhere
on the planet. By 2014 I think you can count on having a functional
barcode library linking barcodes to the binomial names that link to the
accumulated knowledge about them. And I think you can count on having a
"Our job is to reveal how many species there are on the planet and
provide really simple tools to tell one species from another."
< DNA splits >
Unique DNA barcodes for provisional new bird species were obtained from
these look-alike specimens.
< DNA lumps>
These groups of bird species were shown to have virtually identical DNA.
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