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Amphibians wiped out before they are discovered

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Fungal disease drives the loss of 30 species in Panama.

Janet Fang

clip_image001The Panamanian golden frog(Atelopus zeteki)is one of many species being decimalted by chytridiomycosis. Alberto Aparicio/XinHua/Xinhua Predss/Corbis

A Panamanian park has lost around 40% of its amphibian species in the past decade, with some dying out before biologists had even learned of their existence, according to research published today in the Proceedings of the National Academies of Science USA1. Combining genetics with nearly ten years of field surveys, biologists discovered 11 new species, only to find that five of them are already extinct in the area.

"We're losing things before we find them," says Andrew Crawford, an evolutionary geneticist at the University of the Andes in Bogotá, Colombia, and lead author of the study.

The disease chytridiomycosis, caused by the chytrid fungal pathogen Batrachochytrium dendrobatidis, threatens more than 2,800 amphibian species worldwide. Amphibians infected by the disease have skin several times thicker than normal, which affects their ability to breathe and the transfer of electrolytes.

Anticipating the arrival of B. dendrobatidis in El Copé, Panama, as a wave of infection advanced from the northwest of the country, co-author Karen Lips, a biologist at the University of Maryland in College Park, began leading field surveys in the 4-kilometre2 area in 1998. Her team set up transects, walking along 100-metre lines, marking down the species observed and collecting samples. The epidemic hit in 2004, enabling researchers to conduct a before-and-after comparison.

After sequencing toe clippings or liver samples from 297 specimens collected before the decline, the researchers found that the area was home to 63 known species. By using DNA barcoding — which involves sequencing standardized DNA marker fragments to match specimens with known species — Crawford and his co-workers identified a further 11 species that were previously unrecognized.

Thirty of these species are now extinct in the area, including "five that were wiped out before we even knew they were there", says Crawford. This brings the total loss of amphibian lineages to 41%. Naming a species that is already extinct was "pretty sobering", says Crawford.

Branching out

The researchers also looked at amphibian evolutionary history, which considers all the frogs, salamanders and caecilians that have existed over millions of years.

Conservationists use species as a category to describe what needs protecting. The International Union for Conservation of Nature, based in Gland in Switzerland, for example, has an authoritative list of threatened species. But, according to Crawford, it is not always the best measure of diversity, especially when the relationship between species is not very clear. "There are so many debates on whether something is one species or two," he says. "And rather than fight about it, we made an evolutionary tree and looked at what percentage of branches was lost."

clip_image002The disease has caused the extinction of many amphibian species, including at El Copé national park, which has lost over 30 species to the disease.Vance Vredenburg

Crawford and his team mapped out the history and relationships — such as their common ancestors and when they split from other species — of all the species they found in the area. They found that 33% of all the branches in this evolutionary tree are gone — El Copé has lost 33% of the total history of all its amphibians.

"Up until now, we've only had a very crude estimate of what is lost. It has just been, 'We've lost a lot of species,'" says Vance Vredenburg, a biologist from San Francisco State University in California, who recently published on the dynamics of the disease2. Species could have separated from each other in the past 20 years or in the past 20 million years, he says.

"What they did was quantify it," adds Vredenburg. "They took what we knew and added significance."

Crawford and his colleagues also looked at where extirpations occurred in the amphibian tree. Previous studies found patterns suggesting that some lineages and groups are hit harder than others, but in El Copé, the disease hit across the entire range of evolutionary history, wiping out some lineages and not others in a random way.

What now?

"The fungus is moving fast," says Crawford, who is conducting rapid surveys in the easternmost province of Panama before the fungus hits the area.

Animals can be cured with anti-fungal solutions, but the problem is how to introduce healthy populations into the wild without causing reinfections. "There's a lot of hope, hypotheses and preliminary data, but no solution," says Crawford. In the meantime, herpetologists are attempting to preserve animals by removing them from their natural habitat.

Another conservation method being explored is the use of probiotics3. Frogs and salamanders have symbiotic bacteria growing on their skin, defending them against the fungus. Vredenburg and his team are taking bacteria from healthy populations in the wild and culturing them in the lab — hoping to inoculate populations with heavy doses of their own beneficial bacteria, "to give them a big immune boost so that they have a fighting chance".

Amphibians are the oldest class of existing four-legged vertebrates, having been around for 300 million years. "Part of what's so alarming is that these long-term survivors are dropping off the face of the Earth right now," says Vredenburg.

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Animal rights 'terror' law challenged

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Targeted researchers support the legislation, despite free-speech concerns.

Emma Marris

clip_image003Free speech or terrorism? Activists chalk messages.N. Berger/AP Photo

A tough but rarely invoked US law intended to protect researchers from violent and threatening animal-rights activists has stumbled out of the starting gate: last week, a judge dismissed the first prosecution under the law. The decision comes on top of evidence that the legislation has done little to deter illegal incidents, and concerns that it risks restricting free speech.

Yet researchers who have been targeted by activists mostly support the law — and wish that it would be enforced more often and more aggressively. "You could present this as a setback," says John Ngai, a neuroscientist at the University of California, Berkeley, and the university's spokesman on animal research issues. "But this is one step in a lengthy process. The wheels of justice grind really slowly."

The 2008 Animal Enterprise Terrorism Act (AETA), which replaces a less powerful statute, is designed to help end campaigns of harassment against academic scientists. It outlaws property damages at universities and threats that produce a 'reasonable fear' of death or injury for researchers or their relatives.

The law's first major test came in February 2009, when four animal-rights activists — Adriana Stumpo, Nathan Pope, Joseph Buddenberg and Maryam Khajavi — were arrested and later indicted under the AETA, for incidents at the homes of several University of California system researchers in 2007 and 2008. The group, with other protesters, wore bandanas over their faces and wrote messages such as "Stop the Torture", "Bird Killer" and "Murder for Scientific Lies" on the pavement with blue and purple chalk, according to police reports. The protesters allegedly burst through a researcher's door and one of them hit her husband with an object.

But on 12 July, a federal judge dismissed the indictment for being too vague: prosecutors did not say which of the activists' alleged actions violated the law. However, prosecutors are free to re-indict if they can show how particular actions crossed the line.

By classing animal-activist crimes as 'terrorism', the statute has succeeded in bringing more law-enforcement resources to bear on the issue, especially from the Federal Bureau of Investigation, says Frankie Trull, president of the pro-animal-research National Association for Biomedical Research (NABR) in Washington DC.

Yet Trull has been disappointed with the results so far. Several dangerous crimes remain unsolved, including the firebombing of a house and car belonging to researchers in Santa Cruz, California, in 2008, and the March 2009 torching of a car belonging to David Jentsch, a neuroscientist at the University of California, Los Angeles (UCLA). "Why aren't they arresting these guys?" asks Trull. "It is hard to believe that these extremists are so sophisticated that they don't leave any trail."

There are also few signs that the law has been a deterrent. The number of illegal incidents fluctuates wildly (see 'Wrongs in the name of animal rights'), and analyses by groups on both sides of the issue — the NABR and the activist-sympathizing Bite Back magazine — show no clear effect on the number or nature of attacks since the AETA was passed.

Most law-enforcement efforts against animal rights-related crimes in the past decade rely on other legislation. In California, which sees the bulk of US attacks, the state's Researcher Protection Act of 2008 has made it a misdemeanour to publish the names and locations of researchers to encourage crimes against them. Under other state laws, UCLA has been granted injunctions that ban several activists from approaching researchers' homes. Activists have also been successfully pursued under anti-stalking laws.

The strong language of the AETA — which in the Berkeley case raises freedom of speech issues, the judge warned — could be making prosecutors wary of using it. Lawyers for the defendants say that much of the activists' activity — chalking, chanting and leafleting — should be considered protected 'speech', and therefore be exempt from restriction. According to Michael Macleod-Ball, chief legislative counsel of the New York-based American Civil Liberties Union, "Prosecutors need to be careful about how they use this, because the language in the statute is a little squishy."

Researchers who have been the target of attacks don't want prosecutors to give up yet. Jentsch endured lengthy protests at his home after the burning of his car. He thinks that the AETA could deter protesters who are "actively seeking the boundary of protected speech" to harm researchers without getting arrested. But this won't happen until there are more AETA arrests. "I don't see that the AETA has really affected activists yet," says Jentsch. "It has got to be used to aggressively pursue people who have pushed the bounds of behaviour."

Corrected:An earlier version of this story incorrectly implied that the incidents for which animal rights activists were arrested involved only researchers at the University of California, Berkeley. In fact, researchers at the University of California, Santa Cruz, were also targeted.

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6 Responses to “【资讯】灭绝与动物恐吓法”

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