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from NYTimes: Earliest Flowering Plants
bellow i'm reproducing an article in today's NYTimes re: more development in
research on the evolution of earliest flowering plants. hope this is of
interest to the list.
tsuh yang chen, nyc, USA
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NY TIMES
October 29, 1999
Biologists Find Progenitors of Earth's Flowering Plants
Plants--------------------------------------------------------------------------------
By CAROL KAESUK YOON
After more than a hundred years of arguing, theorizing and frustration,
evolutionary biologists have at last answered a question so difficult that
Darwin himself called it the "abominable mystery": how did the world's
flowering plants, the most diverse and important group of plants on earth,
first evolve?
In a highly unusual confluence of discoveries, four teams of researchers
studying plant DNA have independently and simultaneously come up with the
same answer to this highly contentious question, deciphering the earliest
history of flowering plants and identifying the three most ancient groups in
its family tree. The first of the results to be published appears in Friday's
issue of the journal Science.
The three most ancient groups are water lilies, relatives of the spice star
anise and the oldest of all, a group now represented only by Amborella, an
unremarkable bush found only on the South Pacific island of New Caledonia.
Identification of the groups and the drawing of new family trees will allow
botanists to follow with new precision the evolution of many important
characteristics of flowering plants, from their defining trait, the flower,
to their most delicious, the fruit.
The four teams, involving scientists from many universities in several
countries, came to identical conclusions, though the results of only one
team, comprising scientists from Harvard, have been published so far. Between
them, the teams include most leading researchers using plant DNA comparisons
to understand the early history of plants.
"It is the answer," Dr. James Doyle, a paleobotanist at the University of
California at Davis, said of the identification of the three groups and their
arrangement on the new family tree of plants. Dr. Doyle was not involved with
the studies but, like others, he expressed confidence in the results.
"It's all come to a huge crescendo," he said.
Dr. Jeff Palmer, molecular evolutionary biologist at Indiana University who
is a member of one of the four teams, said: "All too often people get results
that conflict with one another and you're left wondering what the truth is.
These studies reach the strong conclusion, and it's the same strong
conclusion. It really is a remarkable event."
Researchers say that in the past a number of different plants have been
proposed as the most ancient, among them magnolias, birches, oaks and the
monocots, a group that includes grasses and lilies.
"Almost anything you could come up with has been suggested," said Dr. Dick
Olmstead, a plant evolutionary biologist at the University of Washington who
is studying the problem with Dr. Sean Graham of the University of Alberta,
who together formed one of the four teams.
Based on the new findings, scientists say the progenitor of flowering plants
-- a group that includes orchids, corn, oaks and cactuses -- was most likely
woody, possibly shrubby or viney, with a flower bearing an unusual female
reproductive structure whose parts were glued together by a sticky secretion
rather than fused into a seamless structure, as they are in modern flowering
plants.
"It's going to really change our view of what the most ancestral type of
flowering plant was like," Dr. Olmstead said.
Each team of researchers took slightly different approaches to determining
the family tree of flowering plants and pinpointing its most ancient groups.
Dr. Olmstead and Dr. Graham studied a large number of slowly evolving genes.
Dr. Douglas Soltis and Dr. Pamela Soltis, a husband and wife team at
Washington State University, and their colleagues looked at fewer genes but
studied those genes in a wide variety of plants.
And in research described in Friday's Science article, Dr. Sarah Mathews and
Dr. Michael Donoghue of Harvard University used a new technique that they
used to look into the group's history. The researchers studied a gene that
had duplicated itself into two copies in the earliest flowering plants,
providing two independent road maps to the evolution of the group -- maps
that, as the researchers expected, turned out to be very similar.
The scientists say the new findings do not indicate which nonflowering plant
sprouted earth's first flower. And, while nearly all researchers have
enthusiastically accepted the new work, a few have sounded cautionary notes
over the answer to this question, which has been so problematic in the past.
For example, Dr. William L. Crepet, a paleobotanist at Cornell University,
said he would not be shocked if there were some shifting around in these
early branches of the family tree as studies continued, but he added, "It
looks pretty good for Amborella right now."
For biologists seeking a window into the early evolution of flowering plants,
the new findings are invaluable. Of particular interest is Amborella, the
bush catapulted from obscurity to botanical stardom.
Sandra Floyd and Dr. William E. Friedman, plant evolutionary biologists at
the University of Colorado, are studying the evolution of a part of the seed,
called the endosperm, that nourishes the plant embryo (or the human who eats
the seed).
To fully understand the evolution of this feature, which is unique to
flowering plants, Ms. Floyd said she and Dr. Friedman were studying the
endosperm in Amborella, using material from the arboretum at the University
of California at Santa Cruz, where the only Amborella in the continental
United States grows.
"These are the types of things that people have been speculating about for
decades, centuries," said Dr. Pamela Soltis of Washington State University,
"and now we can actually address them."