Wednesday, September 05, 2007

Bee Dates Orchids Back To Time Of Dinosaurs

Bee dates orchids back to time of dinosaurs

Mark Henderson, © Copyright 2007 Times Newspapers Ltd.

The earliest evidence of orchids shows that the plants may have coexisted with the dinosaurs.

Scientists have been able to calculate the age of the orchid family with greater accuracy than was previously possible after the fossilised remains of an extinct bee with a mass of orchid pollen on its back were discovered in the Dominican Republic in 2000.

An analysis of DNA extracted from the pollen, led by Santiago Ramirez of Harvard University, suggests that although the fossil itself is 15 million to 20 million years old, the genetic roots of orchids stretch back much further.

Dr Ramirez estimates that orchids appeared between 76 million and 84 million years ago, at a time when dinosaurs such as Tyrannosaurus rex were still living. Previous estimates have variously put the origin of orchids as recently as 26 million years ago and as distant as 112 million years ago.

“Since the time of Darwin, evolutionary biologists have been fascinated with orchids’ spectacular adaptations for insect pollination,” Dr Ramirez said. “But while orchids are the largest and most diverse plant family on Earth, they have been absent from the fossil record.

“Our analysis places orchids far toward the older end of the range that had been postulated, suggesting the family was fairly young at the time of the extinction of the dinosaurs some 65 million years ago.

“It appears . . . that they began to flourish shortly after the mass extinction at the so-called K/T boundary between the Cretaceous and Tertiary periods, which decimated many of Earth’s species.”

While many ancient plants have become fossilised, orchids are largely absent from the fossil record because of several factors. The flowers bloom infrequently and are concentrated in tropical areas, where heat and humidity prevent fossilisation, and pollen, which is easily destroyed, is carried only by insects and animals and never by wind. Details of the discovery are published in the journal Nature.

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