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Radical Findings on Plant Evolution
Worldwide project solves old mystery of how flowers came into being

  Thursday, August 5, 1999

Scientists released yesterday the most complete analysis yet of how the world's million species of plants are related to one another, overturning longstanding theories that the first single-celled algae advanced in size and complexity to become the showy trees and flowers at the pinnacle of plant evolution.

Perhaps most surprising, the five- year effort to map the entire family tree for all plants -- involving more than 200 scientists in 12 countries -- has determined that a rare and previously unheralded tropical flower is the closest living relative of the Earth's first flowering plant.

The unexpected discovery uproots both of the leading theories about what the first flower looked like, and apparently solves what Charles Darwin called the ``abominable mystery'' of how plants made the leap from primitive green monotony to full floral ebullience. That global makeover fueled an explosion in biological diversity among insects and other animals.

``This is the first comprehensive, coordinated, large-scale attempt to reconstruct one of the major branches of life,'' said Brent Mishler, a professor of integrative biology at the University of California at Berkeley and a spokesman for the federally financed ``Deep Green'' project.

The new analysis, presented at the 16th International Botanical Congress in St. Louis, also comes to the jarring conclusion that there are at least three separate plant kingdoms rather than one, as most high school students are taught today.

It finds that plants invaded land not directly from the sea, as many scientists had thought, but from fresh water, where they spent millions of years preparing for the rigors of terrestrial existence.

And it concludes that the many families of green plants on land today descended not from separate evolutionary upstarts but from a single green ``Eve,'' a close relative of which still lives in pristine lakes as it did more than a billion years ago.

Beyond the intellectual gratification that comes with understanding how the world's plants are related, the new findings could have practical benefits, said Peter Raven, director of the Missouri Botanical Garden, which is hosting the weeklong meeting of 4,000 botanists.

For example, Raven said, it makes sense for botanists seeking new medicinal compounds to focus on plants closely related to those already known to have therapeutic properties. But that approach has been hampered by the lack of an accurate family tree.

Conversely, conservationists worried about accelerating plant extinctions want to preserve seeds and other genetic resources from a broad array of plants. But in order to decide where to concentrate their efforts, they need to know which plants represent the most disparate branches of the botanical family tree.

``It's the ability to compare that gives meaning to everything in biology,'' Raven said.


 
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©1999 San Francisco Chronicle   Page A6
 


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