Tuesday, 15 October 2013

The First Flowers

Even the most hostile of deserts can play
host to flowers with just a little rain
The early continents were lifeless. From horizon to horizon red, barren deserts, glittering salt pans and mountains of black volcanic stone covered in thin, poor soils incapable of sustaining even the hardiest of life forms, stretched far and wide.

This all changed around 415 million years ago. As ozone accumulated in the atmosphere, filtering out ultraviolet radiation from the sun, plants made a move onto land.

Verdant landscapes emerged relieving the dusty tones of earth and rock. For hundreds of millions of years this would persist until flowers evolved. Today they are some of the most beautifully toned organisms on Earth. Whole deserts are transformed in days as the occasional shower of rain awakens dormant seeds of florets, creating a carpet of bright petals unrivalled in their beauty by almost any other spectacle in the natural world.

There exists intensive research into the origins of flowering plants, properly called angiosperms. Yet the fossil record for plants is not as extensive as for animals. We have numerous specimens of preserved flowers which indicate that the group first evolved around 140 million years ago during the Cretaceous period. Yet new evidence catapults the date for the origin of angiosperms back by an incredible 100 million years. This is massive in evolutionary terms.

The 240 million year old fossilised pollen which may
come from the oldest angiosperms on the planet
By examining drilling cores taken from rocks at Weiach and Leuggern in northern Switzerland, Professor Peter Hochuli and Susanne Feist-Burkhardt from Palaeontological Institute and Museum at the University of Zurich, have found fossilised pollen which indicate that angiosperms actually evolved during the early Triassic, some 240 million years ago.

Using a form of laser scanning microscopy, they obtained images of six different types of pollen which bore a strong resemblance to that found in modern day flowering plants.

Molecular studies, which use rates of mutation, have given a wide range of dates for the origin of angiosperms. These, however, are calibrated using fossil evidence. Hochuli and Feist-Burkhardt's fossils will prove invaluable in refining the parameters used to calculate when flowering plants first evolved. 'That is why the present finding of flower-like pollen from the Triassic is significant,' said Professor Hochuli.

Exactly what the plants would have looked like is debateable. It is hard to tell from near microscopic grains. Even so, the team was able to make some inferences based on the environment which the pollen grains came from and their structure. Similar pollen fossils of a similar age were found in 2004 near Spitzbergen in the Arctic Sea. 240 million years ago, both regions occupied very different climate zones: one dry, one subtropical.

Modern day pollen.
The pollen-producing plants, therefore, must have adapted to cope with a variety of temperatures and degrees of aridity. The shape of the pollen itself suggested that it was spread by insects, most likely beetles as bees and their close relatives would not evolve for another 100 million years.

Perhaps what is most interesting is the proximity of the date of the pollen to the Permian extinction event which occurred just 10 million years before.

There is a strong possibility that angiosperms evolved to fill newly freed ecological niches, exploiting the lack of competitors to develop a new lifestyle based around insect pollinators (intriguingly insects were one of the few groups not to greatly suffer during the extinction). It is good to think that out of the destruction of the Permian extinction came the first flowers, bringing colour back to a world which had been brought to the very brink.