SCIENCE

Monday, October 9, 2006

Tropics Nurture Marine Species

The tropics serve as both the engine of new biodiversity and a "museum" where older species are preserved, according to a new research that may settle a long-running scientific debate.

The study, based on fossil records dating back 11 million years, documented that many species evolved first in the tropics before moving to higher latitudes. Three researchers -- University of Chicago geophysicist David Jablonski, University of California at San Diego ecologist Kaustuv Roy and University of California at Berkeley biologist James W. Valentine -- reached their conclusion by tracing the lineages of 150 types of bivalves, a class of marine life that includes clams, scallops and oysters.

"The world is connected. It's a global village, even for organisms," Roy said in a statement. "Along the California coast most of the marine species belong to lineages that originated in the tropics."

Over the past 11 million years, the scientists reported in last week's issue of the journal Science, more than twice as many bivalve lineages arose in the tropics as in higher latitudes. These organisms also had a higher chance of survival in the tropics: 107 varieties of bivalves they surveyed outside the tropics went extinct, compared with just 30 in the tropics.

"It's a really striking, surprising pattern," said lead author Jablonski. "I think we've killed the idea that the tropics is either a cradle or a museum of biodiversity. It's both."

-- Juliet Eilperin

Dogs' Prenatal Sense of Smell

Dogs are famous for their sense of smell. But only now, with the publication of a peculiar experiment, can scientists say with assurance that dogs are already sniffing and smelling while still in the womb.

Deborah L. Wells and Peter G. Hepper of the canine behavior center at Queen's University of Belfast knew that "prenatal chemosensory learning" -- the ability to differentiate among smells before birth and develop preferences that persist afterward -- had already been documented in other animals. Some experts have theorized that prenatal olfactory learning helps newborns recognize their mothers and may help prompt suckling behavior.

Yet the phenomenon had never been tested in dogs, despite their reputations as world-class sniffers.

The researchers enrolled 22 pregnant dogs in a series of studies in which some were fed food spiked with aniseed. Immediately after birth, pups were taken briefly to a quiet area and presented with a pair of cotton swabs -- one wetted with a trace of aniseed and the other with distilled water.


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