New Research Shows That Early Bees Were Fussy Pollinators

Insect pollination has fuelled great diversification
in  the angiosperm family and vice versa

Plants and insects have formed a myriad of complex symbiotic relationships. Pollinators have optimised themselves for the collection of nectar while flowers have developed enticing scents and colours to attract in would-be pollinators.

Many insects will visit multiple flower species. They are not fussy eaters. Their only goal is to obtain as much nectar as possible. Some insects, however, are much more selective in their diet, visiting only one particular species in their quest for nectar, and occasionally, going to extraordinary lengths to do so.

Such specificity is certainly a risk as the abundance of the two species will be closely linked, with changes in each party directly affecting the other. The major benefit, however, is the development of a highly effective symbiosis. A recent study conducted by an international team of researchers has shown that bees have enjoyed these close symbiotic relationships for millions of years. The research was conducted on fossils from the Messel Pit in Germany. During the Eocene epoch 50 million years ago, the Messel area enjoyed a tropical climate. Formed by sediments deposits in a volcanic lake, the Messel pit oil shales preserved a plethora of species which were overwhelmed by toxic gases emanating from the lake

Fossils from the site are preserved in perfect detail, allowing creatures as delicate as insects to be studied in great depth. 'For the first time, we are taking advantage of this circumstance in order to get a closer look at the pollen on the bees' bodies,' said Dr. Torsten Wappler from the Steinmann Institute for Geology, Mineralogy and Palaeontology at the University of Bonn. The back legs of bees are long and have comb-like structures which allow them store pollen. The front legs are used to comb pollen out of their body hair and transfer it to their back legs.

Fossil bees from the Messel Pits and microscope images
of some of the pollen types found on their legs

This only works, however, if the front legs can easily reach the pollen.

'The bushes where the worker bees collected food for their larvae all had a similar blossom structure,' said Dr. Wappler. 'After they visited those blossoms, the pollen mainly stuck to parts of their bodies where it was easy to transfer to their legs.'

Analysis of the fossils showed that the pollen on the heads, chests and abdomens came from a variety of plant species. The pollen on their back legs came from primarily evergreen bushes. Evergreens produce similar blossoms. The arrangement of the pollen-bearing structures is therefore similar across the group and so produces the same distribution on a bee's body.

'This was a good strategy for the bees,' concluded Dr. Wappler. 'When they were looking for food for the larvae, they visited blossoms that offered a high yield with little effort. On the way there, on the other hand, they ate whatever they happened to find. So they didn't waste any time looking for especially delicious or nutritious food.'

These simple patterns are clues in the fossil record. They point to potentially complex biological interactions among long dead species. Improvements in technology will eventually highlight previously overlooked patterns to allow us to build up a much richer picture of the biosphere's past.