Saturday, 7 June 2014

The Birds and The Bees

The White Campion uses explosive pressure to eject seeds from its pods
Flowers have developed extraordinary methods of reproduction. From feathery pollen which float on the winds to pods which burst open under pressure to fire out seeds covering metres of ground.

These diverse methods have been honed by hundreds of millions of years of evolutionary tinkering. Yet the most successful are the pollinators: the insects. They are an integral part to almost every ecosystem.

At some point during the Cretaceous period plants bought into the vast transportation network that they formed. Flowers developed adaptations to lure insects and brush them past anthers loaded with pollen. A visit to another flower resulted in pollen transfer. Plant diversity has increased ten fold as a result of this unintentional effort.

Yet insects are not the only pollinators. Go to the jungles of Ecuador and you find long, red trumpet-shaped flowers. After a short while something remarkable happens. A hummingbird will come along: it may be small or large with a bill twice the length of its body. It will seek out nectar from the very heart of the flower, at the base of the trumpet. A small amount of pollen will brush off on its wings or the base of its neck as it feeds. This will be transferred to another flower of the species. Birds are pollinators as well. Now new evidence shows just how old this relationship is.

47 million years ago the Messel Pits in Germany were covered by a volcanic lake, fringed by tropical forests. Animals and plants living in the area were regularly overcome by gases from the lake and buried on its bed. Specimens are preserved in a wealth of detail. Indeed we have been able to reconstruct the ecosystem to an unprecedented degree. A link to this ancient world has been added by a team of researchers from Senckenberg Research Institute in Frankfurt: they uncovered a bird fossil, Pumiliornis tessellatus, with traces of pollen.

Pumiliornis tessellatus. The circles show the location
of the pollen grains within the stomach
Detailed analysis of its stomach contents revealed the presence of pollen grains. 'This is another discovery that underlines the unique significance of the Messel fossil site,' said Dr Volker Wilde. 'Not only does the presence of pollen offer direct evidence of the bird's feeding habits, but it shows that birds already visited flowers as long as 47 million years ago!.....We were able to identify two different types of pollen, which is the first conclusive proof of nectarivory,' explained Dr Gerald Mayr.

An examination of the bird's anatomy showed that it had certain similarities to modern hummingbirds. At just 8 centimetres in length and 5 to 10 grams in weight, it was diminutive. Despite its small body size, it had a long needle-like bill, with elongated nostrils designed to increase bill flexibility. These traits allowed it to search for nectar deep within flowers, together with a backwards turned toe to grip the edges of petals and leaves. While its anatomy is not complete enough for it to be distinctly classified it is quite similar to modern nectar-feeding avians.

Understanding the relationship between plants and birds is of the utmost importance. With the decline of bees and increased use of pesticides, which not only kill crop pests but other, harmless pollinating insects vital to the well-being of ecosystems, birds may be the lynch pin holding countless species together. Understanding their origins as pollinators, and how that relationship has changed over evolutionary time in response to changes in climate and biodiversity, will aid conservation efforts today.