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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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High on Speciation
15 March 2007 (All day)
It seems like a no-brainer: To find out where most new species arise, see where most of them live. Take the tropics, home of more than half the known organisms on the planet. For nearly a century, researchers have assumed that new species are constantly popping up here, while speciation is far more stagnant at Earth's relatively deserted poles. But a new study claims the opposite: Species evolve much more readily at higher latitudes. It's just that the new arrivals die off so fast that most of them never get counted.
For a plant or animal to form a new species, something must divide its population so that individuals go their separate ways and develop unique adaptations over time. The barrier needn't be physical: When the polar bear split from the Grizzly bear about 300,000 years ago, for example, scientists think a change in climate drove them apart. But as climate can create, it also can destroy. Harsh environments can wipe out new species that can't adapt. Pondering that dual role led zoologists Jason Weir and Dolph Schluter of the University of British Columbia in Vancouver, Canada, to wonder whether Earth's poles were really anathema to speciation.
The pair studied 309 pairs of bird and mammal sister species (the most closely related pair from a common ancestor) living from the tropics to the poles. DNA analysis revealed that, on average, birds and mammals near the equator diverged from a common ancestor 3.4 million years ago; in contrast, those near the poles diverged less than 1 million years ago. That means new species pop up more frequently at high latitudes than they do at low ones, the team reports tomorrow in Science. Biologists had assumed that the temperate weather near the equator was a boon to speciation, the authors note, but these mild conditions may just be keeping old species around longer. Harsh conditions near the poles, in contrast, kill off many of the new species that arise, creating the illusion of less speciation.
"It's a surprising result," says phylogenetic biologist John Wiens of Stony Brook University in New York. "I think it'll get people talking."