From: Kathleen Wong, California Academy of Sciences
Published October 14, 2004 12:00 AM

Genetically Modified Pollen Travels Frighteningly Far and Other Stories

Genetically Modified Pollen Travels Frighteningly Far


Bioengineered plants can sow their genes over many kilometers in just a single season, according to a new study. The findings give ammunition to those concerned about modified genes contaminating wild populations.


In the study, Lidia Watrud and colleagues at the U.S. Environmental Protection Agency monitored a field planted in creeping bentgrass with genes conferring resistance to the herbicide Roundup. Planters of sentinel grasses were placed several kilometers away from the field. After pollination season, the experimenters collected both wild and sentinel seedlings sprouting in a radius of several kilometers and treated them all with Roundup. Those that survived were checked for the presence of the modified gene.


The scientists report in the Proceedings of the National Academy of Sciences that many of the seedlings growing within a two kilometer radius of the field were contaminated with the modified gene. More worrisome still, wild grasses up to 14 kilometers away from the field and potted sentinel plants up to 21 kilometers downwind produced transgenic seed as well.




Glacier Melt Accelerates in Antarctica


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The breakup of a vast ice sheet in Antarctica has accelerated the melting of five nearby glaciers, according to a new study. In 2002, global warming melted the ice tethering the 3,250-square-kilometer Larsen B ice shelf to Antarctica. Since then, scientists have kept a close eye on the region to monitor any aftereffects.


Now researchers at the National Snow and Ice Data Center in Boulder, Colorado, report that three glaciers held back by the shelf moved eight times faster in 2003 than they did in 2000. Two other glaciers have nearly tripled their pace. All are in the process of plunging into the Weddell Sea. In addition, the elevation of these glaciers has plunged by as much as 38 meters a mere six months after the ice shelf's collapse.


The researchers report in the journal Geophysical Research Letters that as these and other Antarctic glaciers disintegrate, the result will be an alarming rise in world sea levels.




Moisture and Methane Hint at Life on Mars


Traces of methane and water hugging the lower atmosphere of Mars are buoying hopes that life exists the Red Planet. The Mars Odyssey and Mars Express spacecraft have found water vapor and methane together in three regions along the planet's equator.


Methane breaks down into water and carbon dioxide relatively quickly. For this reason, scientists say, a source must be actively producing the gas. Volcanoes, hydrothermal vents, or microbes could all be responsible. But the presence of methane and water together encourage bets on bacterial life.


Bacteria often emit methane as a byproduct of their metabolisms, while water is thought to be necessary to support life. The areas of interest, known as Arabia Terra, Elysium Planum, and Arcadia-Memnonia, are all underlain by a layer of ice several feet below the soil's surface. Scientists say the bacteria may be living in a layer of water located beneath the ice.




Global Warming Influences Evolution


Rodent remains entombed in a Rocky Mountain cave have offered a sobering lesson how global warming can affect the course of evolution. Lamar Cave in northeastern Yellowstone National Park has sheltered small animals for at least 3,000 years.


Elizabeth Hadly of Stanford University has painstakingly sifted through tens of thousands of their moldering bones for 20 years to determine how these rodents were affected by a period of historic climate change. From 850 to 1350 AD, the Medieval Warm Period heated and dried the rodents' Rocky Mountain habitat.


Hadly now reports in the journal PLoS Biology that the warming trend imposed dramatic changes on at least two cave residents: pocket gophers and montane voles. The heating trend cut populations of both rodents nearly in half. The gophers became inbred, as their subterranean habits left them unable to venture far in search of mates. The voles, on the other hand, continued to mix with animals from farther away. The steady infusion of outside blood kept their genes remarkably diverse. Both rodents' numbers exploded again during the subsequent Little Ice Age.





Bachelor Frogs Get the Last Laugh


The odds are against male European brown frogs finding a mate. There are four to 10 times as many male frogs as females in the ponds of the upper Pyrenees mountains.


But those suitors who are unsuccessful in love just won't quit. During a typical mating ritual, the male clasps an egg-heavy female until she begins to lay. At that point, he covers the clutch with his sperm and swims away.


Scientists report that males desperate to father future generations will clasp and fertilize masses of eggs in hopes of siring any missed by the first male. The strategy can be quite successful, as up to 84 percent of all clutches have been fertilized by more than one papa.




High Altitude Human Evolution


An example of human evolution in action has turned up amid the thin air of the Himalayas. A gene that improves oxygen-carrying capacity is spreading with surprising rapidity through Tibetan communities.


Cynthia Beall of Case Western Reserve University in Cleveland, Ohio, studied the survival of Tibetan infants living above 4,000 meters. The researchers interviewed thousands of villagers living at high altitudes to obtain their pregnancy histories and reconstruct their family trees. The researchers then estimated the oxygen concentration in the blood of each person using a noninvasive technique often used in hospitals.


Taking into account factors such as age, smoking habits, and illness, the scientists found some families tended to carry up to 10 percent more oxygen in their blood than others. Women with high oxygen levels lost an average of 0.4 children before age 15, compared to 2.5 child deaths among women with normal oxygen levels. Inheritance patterns suggest the trait is carried by a single gene, although no one is sure how it works. But given the trait's selective advantage for survival, researchers report in the journal Nature that the gene should spread throughout the Tibetan population within 2,000 years.





Related Links


Genetically Modified Pollen Travels Frighteningly Far: BBC / Scientific American


Glacier Melt Accelerates in Antarctica: Yahoo Daily News (Reuters)


Moisture and Methane Hint at Life on Mars: New Scientist / Nature News


Global Warming Influences Evolution: San Francisco Chronicle


Bachelor Frogs Get the Last Laugh: Los Angeles Times


High Altitude Human Evolution: Nature News





Source: California Academy of Sciences


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