Scientists commonly use electricity to increase the permeability of bacterial cell membranes, making it easier to insert DNA. Now Sandrine Demanèche’s team at the University of Lyon has provided the first evidence that nature may have been wise to this trick all along.

The researchers seeded soil samples with the E. coli bacterium, as well as fragments of DNA containing genes for antibiotic resistance. They zapped the soil with a simulated lightning strike, and found that many of the bacteria had acquired the resistance genes.

Bacteria are already known to take up and use foreign DNA released into the environment when other organisms die. Scientists knew this “horizontal gene transfer” occurs naturally in soil, but thought it was relatively rare. However, recent genomic research indicates that this gene take-up is widespread and has played a major role in the evolution of the bacterial genome.

“This result might help explain the discrepancy between the very low observed rates of gene transfer and the apparently wide distribution of DNA sequences among bacteria,” says team member Timothy Vogel.

Lightning may seem relatively rare, but there are about a hundred flashes a second around the planet. Ground strikes almost always create currents in the surrounding soil similar to those from the simulated bolts, Vogel says.

Journal reference: Applied and Environmental Microbiology (vol 67, p 3440)

Parrots are among the most endangered birds – nearly one third of species native to the neotropics are considered at risk of global extinction. While habitat loss is behind the decline of many species, the new findings suggest poaching may be as big a threat.

“We’ve really had very little handle on what is going on with the illegal trade,” says Steve Beissinger, of the University of California, Berkeley. “This study gives us some feeling for what the levels of poaching are and which species are most affected. For some the rate is low, but for some of the larger and more valuable species it’s startlingly high.”

Biologists Timothy Wright of the University of Maryland at College Park and Catherine Toft of the University of California in Davis led a team which analysed data from 23 separate studies into parrot nesting conducted over the past 20 years. Together, the studies documented the success or failure of 4200 nesting attempts by New World parrots.

Across all the studies, poachers ruined 30 per cent of nests. Four species, including the Yellow-crowned Amazon, lost more than 70 per cent of their nests.

Machete blow

Usually, says Toft, the cause of nest failure was unambiguous. “Humans leave distinctive evidence of their work,” she says. “Trees are climbed with ladders and spikes, and nest cavities are destroyed with a machete. This kind of evidence usually rules out other possible predators.”

Beissinger has also produced a separate report, due for publication later this year, on the legal export of parrots as regulated by the Convention on International Trade in Endangered Species (CITES). He found that 1.2 million parrots were legally exported from 1991 to 1996, with most originating in Central and South America.

In the US, the 1992 Wild Bird Conservation Act bans the import of CITES-listed birds. But there are no equivalent laws in Europe and Asia, which have now become the biggest markets for wild parrots. This legal trade provides a smokescreen behind which illegal poachers operate. “The legal and illegal trades thrive together,” says Toft. “The markets in Europe and Asia remain open.”

Hyperbole after hyperbole

Mike Reynolds, director of the World Parrot Trust in Britain, says the new data will help to reinvigorate efforts in Europe to impose tighter restrictions on the import of threatened parrot species.

But Benny Gallaway, president of the American Federation of Aviculture, says a regulated, sustainable harvest of birds may be a better solution.

Gallaway also questions whether the new study really provides evidence that poaching is as widespread as the researchers claim. “I’ve seen hyperbole after hyperbole presented by the conservation groups, which only alienates many of the people interested in the conservation of birds.”

More at: Conservation Biology (vol 15, p 1)