Saturday, 19 May 2012

Ancient Amber Insects Are The Oldest Evidence Of Pollination

Synchrotron reconstruction of the two Gymnopollisthrips species
The relationship between flowering plants and insects is one of the most fundamental on Earth. The role of bees, beetles and their relatives as pollinators has driven the evolution of not only the arthropods, but reptiles, mammals and birds.

Flowering plants first evolved some 150 million years ago. The closest living relative we have to those evolutionary firsts is a small flower called Amborella trichopoda. The first insects are far older coming in at over 400 million years old.

Palaeontologists have now discovered the oldest evidence of arthropod pollinators on Earth. The two 110 and 105 million year old pieces of amber were uncovered from fossiliferous strata in northern Spain. They were stored for a time at the Museo de Ciencias Naturales de Álava before analysis of the fossils began. A view through the lens of a microscope revealed the presence of six female, two millimetre long thrips, properly known as thysanopterans, which came from a completely unknown genus.

A reconstruction of Gymnopollisthrips attached to the ovum of a ginko
Further study separated them into two species: Gymnopollisthrips major and Gymnopollisthrips minor. Yet what made the insects most interesting was hundreds of microscopic pollen grains stuck to the legs.

To reconstruct this frozen event in time, the amber pieces were taken to the European Synchrotron Radiation Facility (ESRF). The machine consists of a circular particle accelerator which pumps out electrons close to the speed of light focused on the specimen.

The particles have so great an energy that they can penetrate solid rock, allowing incredibly detailed reconstructions of fossils to be built up. The team found that the pollen grain came from a species of cycad or ginko, a tree which dominated the Cretaceous landscape. 'This is the oldest direct evidence for pollination, and the only one from the age of the dinosaurs,' study researcher Carmen Soriano said in a statement. 'The co-evolution of flowering plants and insects, thanks to pollination, is a great evolutionary success story.' The specimens already showed signs of their future adaptations, namely ringed hairs on the legs designed to pick up increased amounts of pollen.

The only piece left out of the puzzle is what the insects got in return for their services. The team believe that the pollen was probably food for the thrips' larvae.