First Record Of 1 Million Year Old Pollinating Insects Discovered
May 16, 2012

First Record Of 1 Million Year Old Pollinating Insects Discovered

A new study, conducted at the European Synchrotron Radiation Facility (ERSF), details the first recorded cases of pollination by insects. Scientists discovered many insects coated in specks of pollen within two pieces of amber dating back to 110 to 105 million years ago in northern Spain. Amber is the only medium that can contain such highly detailed features such as pollination over millions of years.

The team of international scientists includes Xavier Delclòs from the University of Barcelona, Enrique Peñalver and Eduardo Barrón from the Instituto Geológico y Minero de España in Madrid, and Andre and Patricia Nel from the Muséum national d'histoire naturelle in Paris. The team also includes Conrad Labandeira from the Smithsonian Institution, Washington DC and Carmen Soriano and Paul Tafforeau from the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

Nearly eighty percent of all plants and trees today require an insect to transport pollen in order to reproduce. Although pollination is more commonly known to occur in flowering plants, it is also the means of reproduction for seed producing plants including conifers, also known as gymnosperms. Bees and butterflies are the most widely known pollinators, but other insects including thrips, beetles, and flies have adapted to pollinating plants in order to gain access to the plants pollen as food.

Found in Basque country in Northern Spain over the last twenty years, samples of amber dating back from 110 to 105 million years ago in the Lower Cretaceous period have brought to light a number of new plant and animal species, particularly insects. Among the fossilized species found were small insects commonly known as thrips (thysanopterans) who are a mere .07 inches in length. These creatures eat plant material and pollen, and are highly effective pollinators.

The six female thrips studied, covered in hundreds of pollen grains, have specialized hairs with rings that enable them collect large amounts of pollen, and these are highly similar to the hairs that domestic bees have on their bodies.  The tiny pollen grains display a natural ability to stick to insects. Using synchrotron X-ray tomography at the ESRF, one specimen was studied in order to see the dispersal of pollen on its body. Researchers found that the pollen most likely came from a type of ginkgo tree or cycad. These trees are “living fossils” with very few known to science. Male gingko trees generate pollen cones, while females make ovules that turn into seeds once pollinated.

Although the exact reasoning for the thrips to accumulate and carry the pollen of the Gingko is unknown, one theory can be assumed. The Gingko tree benefits from an evolutionary selection that stops the thrip hair from growing, so one explanation suggests that the thrip larvae were fed pollen and that they were kept within some form of a female Ginkgo tree. This indirect pollinating process created a relationship where the larvae could remain safe from harm and the female Gingko could reproduce.

Lead researcher Carmen Soriano stated, "This is the oldest direct evidence for pollination, and the only one from the age of the dinosaurs. The co-evolution of flowering plants and insects, thanks to pollination, is a great evolutionary success story. It began about 100 million years ago, when this piece of amber fossil was produced by resin dropping from a tree, which today is the oldest fossil record of pollinating insects. Thrips might indeed turn out to be one of the first pollinator groups in geological history, long before evolution turned some of them into flower pollinators."

The study is published in this week's online issue of the journal Proceedings of the National Academy of Sciences (PNAS).