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Your orchid is related to WHAT? Changing that family tree.

  • To: "Agardenchat" gardenchat@hort.net
  • Subject: [CHAT] Your orchid is related to WHAT? Changing that family tree.
  • From: "Bonnie Holmes" holmesbm@usit.net
  • Date: Mon, 30 Jun 2003 17:51:09 -0700

Since the recent discussions have included orchids...thought this might
be of interest.  B

An orchid by any other name: Asparagus?

The New York Times

NEW YORK -- Orchids can be elegant, gaudy, lurid and even downright
bizarre. While the unusual flowers of these species have excited plant
lovers for centuries, they have also made it difficult for evolutionary
biologists to place them in the plant family tree and identify their
closest relatives.

Now, scientists say, studies of the DNA of orchids are revealing a host
of surprises, chief among them, that orchids are actually part of the
asparagus group, closer kin to these vegetables than to the other,
flashier, flowering plants they had been placed with before.

"They're so weird, so different from everything else," said Dr. Ken
Cameron, orchidologist at the New York Botanical Garden in the Bronx.

At the same time, scientists are finding that orchids, long thought to be
the recent product of plant evolution, are actually quite ancient, having
emerged more than 90 million years ago.

It is often easy for experts to pick out an organism's closest relatives,
but sometimes -- as with orchids -- appearances can point in many
directions and no direction at all.

One problem is that orchid flowers have undergone striking evolutionary
elaborations, evolving myriad forms and devices, sometimes to entice very
particular animal pollinators. In the process, elements of flower
structure that may have pointed to the group's evolutionary history have
been distorted or lost.

One particular oddity of orchid flowers is their highly unusual
reproductive structure, the normally separate array of reproductive parts
having evolved to be fused together inside a typical orchid bloom.

"You look inside an orchid, and say, 'Where are all the parts?'" said
Cameron. "It doesn't look like anything else."

By looking at DNA, researchers were able to free themselves from limits
of vision. Comparing instead a wide variety of genes both among the
orchids and between orchids and the other flowering plants, Cameron and
colleagues found that the orchids fell squarely within the so-called
Asparagales, the group that includes asparagus.

"People found it hard to believe," Cameron said. But the Asparagales is
large and diverse, containing amaryllis, onions, irises, daffodils as
well as agaves and yuccas.

Scientists say the evolutionary history of orchids has also been obscured
by the oddities of their pollen and seeds.

The pollen of most plants is nearly indestructible and many plant seeds
are extremely tough, providing perfect material to be preserved in the
fossil record. By contrast, the pollen and seeds of orchids are typically
extremely delicate.

"Unlike any other group of plants," said Dr. Mark Whitten, a botanist at
the Florida Museum of Natural History, "there just isn't any reliable
fossil record. With other groups you can find a fossil and conclude that
the group must be at least that old or older. But with orchids it's been
pretty much sheer speculation."

Now, when DNA data are used to build an evolutionary tree of the plants,
they show that orchids branch off fairly early, the first among the
Asparagales plants, meaning they are the oldest in that group. Orchids
also branch off before the palms. Because there are palm fossils that are
90 million years old, scientists know, orchids must be at least that old.

 Bonnie Zone 6+ ETNholmesbm@usit.net  

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