May 18, 2012 | 5
A hundred million years ago, everything looked quite different. There were dinosaurs on land and gigantic creatures in the sea, and the continents were arranged quite differently. But one thing would be familiar to the modern eye: pollination. Recently, scientists found pollen grains on tiny insects preserved in amber from the Cretaceous period, providing the oldest known record of pollination.
Today, pollination is all around us. Over 80 percent of plant species depend on insects to transfer little nuggets of pollen from the male to female parts of flowers for reproduction. Many flowers have specialized parts to attract insects to them, and many insects have corresponding hairs adapted to gathering and carrying pollen. But it wasn't always that way—pollination has evolved over millions of years, and probably began at the beginning of the Cretaceous, perhaps even with insects like these.
The tiny insects here belong to a group called thrips—critters with fringed wings that are less than two millimeters long. Six of the little bugs were preserved in the amber that the researchers found, and on them hundreds of pollen grains, probably from a cycad or ginkgo tree. The work was published in Proceedings of the National Academy of Sciences.
Finding these thrips sheds some light on how early insects were pollinating plants, and why. The thrips had little hairs on their bodies, perfect for collecting pollen, but they didn't evolve those hairs just to help plants out. Instead, the researchers think, the species fed their larvae with the pollen, and those larvae probably lived in the female parts of ginkgo and cycad plants. So the insects would go to the male parts of the plants, gather the pollen grains, and bring them back to their larvae on the female organs. In the process, some of that pollen fertilized the trees, setting off a chain of evolutionary adaptations in insects and flowers that continues to this day.
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