Monday, 8 August 2011

A New Facet On The Great Dying Paradigm

The eight metre tall fungus Prototaxites evolved during the
Devonian, when the land first became inhabitable. Fungi
could have become massive, self contained communities in
just a few million years, large enough to destroy entire forests
There is a new theory that highly aggressive fungi helped destroy huge areas of Permian forest and ultimately, made a significant contribution to the massive Permian extinction event. A common feature found in Permian rocks of all kinds are long, filamentous structures that scientists now believe are the remains of hyphae - the name given to fungal 'cells'. It is thought that they might belong to the mycetic group Rhizoctonia. Modern Rhizoctonia are plant pathogens and are responsible for many common root, stem and foliar diseases.

The remains of the possible hyphal
cells, displaying signs of sclerotia
We know that the main trees in the Permian forests were conifers. We also know that during the Great Dying, conifers almost disappeared and did not recover until around 5 million years later in the Triassic period. The possible hyphae fossils also show signs of structures that are similar to entwined bundles of hyphal bodies known as sclerotia. Sclerotia are energy storage structures that allow fungi to survive in extreme conditions such as the Permian extinction event.

When entire forests are threatened by extreme ecological events, organisms such as Rhizoctonic fungi can cause extreme damage and cause the forest to collapse entirely. The fungi would store the energy in resting structures and go into a form of stasis until ecological conditions reached a sufficient level of stability to maintain life above ground. The Permian Great Dying would have been a text book example of this scenario. Firm evidence of this theory has yet to arise, but it does have several salient points and some fossil evidence to back it up.