In a scene straight out of "Jurassic Park," scientists have discovered the remains of an extinct bee with a piece of orchid pollen stuck to its back inside a chunk of amber which affirms orchids bloomed earlier than expected, some 76 million to 84 million years ago.
"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," said lead study author Santiago Ramirez of Harvard's Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology.
The fossil specimen was found by a private collector in the Dominican Republic in 2000, but it wasn't until 2005 that Ramirez and his colleagues got their hands on it. After analyzing the position and shape of the pollen, the scientists placed the orchid, dubbed Meliorchis caribea, within one of five living subfamilies of orchids.
They decided the pollen was deposited on the stingless bee (Proplebeia dominicana) during active pollination. And in order to transfer the pollen packets to the bee's posterior, the orchid bloom must have been shaped in a particular way in which the anther (the pollen-containing flower part) was bent, the scientists say.
The specimen, described in the Aug. 30 issue of the journal Nature, is one of very few fossils that illustrate directly the relationship between a plant and its pollinator, a phenomenon that has fascinated biologists since the time of Darwin.
By comparing DNA from the pollen sample with DNA from other orchid species, researchers estimated the specimen to be between 15 million and 20 million years old. The so-called molecular-clock method is based on an idea that differences between the DNA molecules of particular species is a measure of how long the two groups have been evolving independent of one another.
The results revealed certain groups of modern orchids evolved early during the rise of the plant family. For instance, they found present-day orchids in the genus Vanilla arose about 60 million to 70 million years ago.
Scientists say the orchid species began to diversify and flourish soon after dinosaurs went extinct.
Source:Xinhua/agencies
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