It is hard to imagine large swathes of forests on land made up of anything other than plants, isn’t it? Just thinking of giant mushrooms sprouting from the earth, dwarfing everything else by a long shot seems like a scene straight out of Alice in Wonderland!
Fungi are among the earliest creatures to appear on land. Here, the fruiting bodies of a fungus emerge through a decaying wood stump in Hunsur, Karnataka. Photo: Purva Variyar
But, long before plants ventured out from the sea, fungi had already established their grand presence on terra firma. Plants first inched their way on to land around 440 to 420 million years ago. These early terrestrial plants began to grow around the edges of water and may have been moss-like in appearance and only a few centimetres tall. As these plants emerged on land, they would have been met with formidable giants in the form of fungi rooted in the earth and towering up to 6-8 metres in height, with whom they would have had to battle for space and resources. Paradoxically, it was fungi that laid the foundation for the evolution and propagation of plants as well as animals. Without them, terrestrial plants or animals wouldn’t exist! Fungi set the stage.
Fungi were among the earliest creatures to advance onto land. Like every other terrestrial organism, origins of the fungi lie in the sea. They first made landfall on the supercontinent Rodinia as early as 700 million-1,000 million years ago. They would have started off small, but over the next several hundreds of millions of years, fungi grew into giants. Around 420 to 360 million years ago, during the Devonian period, megafungi such as the Prototaxites took over the landscape and were the largest terrestrial organisms at the time, reaching heights of up to 8 m. With a few relatively short trees in sight, fungi of various shapes and sizes and magnanimous proportions collectively formed forests of their own, towering over everything and everybody. Plants were yet no match for the fungi. This was a time when early arthropods such as millipedes, centipedes, arachnids as well as the earliest insects were staking their claim outside water.
Palaeontologists have over the past century unearthed curious looking fossilised logs or spires of a large organism we now identify as Prototaxites. But, at first, these fossils stumped even the brightest scientific minds. In the century that followed the first discovery of the giant Prototaxites fossils in 1859, confusion reigned with regards to its identity. Scientists claimed the fossils to be that of lichen or algae, while some rightly surmised them to be fungus. But, the scientific community wasn’t convinced. Something didn’t add up.
One of the largest Prototaxites specimen discovered by Dr. Charles Meissner of the United States Geological Survey Mission in Saudi Arabia in 1987. It was 4.2 m. long and 1.2 m. wide. Photo: Charles Meissner/USGS (1989)
In 2001, curator at the National Museum of Natural History in Washington, D.C., Dr. Francis Hueber, resurrected this controversial subject and thoroughly studied the internal structure of the organism and declared the Prototaxites fossil to be that of a fungus. “Fran Hueber has contributed more to our understanding of Prototaxites than anyone else, living or dead. He built up a convincing case based on the internal structure of the beast that it was a giant fungus, but agonised over the fact that he was never able to find a smoking gun in the form of reproductive structures that would convince the world that it was indeed a fungus,” scientist Carol Hotton, of the National Museum of Natural History said in a statement in 2007, after she and her co-researchers would lay this century and half worth of speculation about the organism’s true identity to rest. The scientists at the University of Chicago and the National Museum of Natural History, used chemical analysis to finally confirm that this mysterious organism was indeed fungus. Reuters while reporting on the historic find called the Prototaxites the “Godzilla of fungi”!
Why did these fungal beasts grow to be so big, after all? “I’ve wondered whether it enabled Prototaxites to distribute its spores widely, allowing it to occupy suitable marshy habitats that may have been patchily distributed on the landscape,” Hotton added.
But, this land domination of fungi over plants was short-lived, geologically speaking. Within a few (about ~10) million years of plants arriving on land, vegetation began to take over. Fungi could no longer compete with the incredible, new adaptations in plants. Plants were producing lignin, a strong, hardy material which helped in better transportation and storage of water and nutrients, and could carry a lot of weight without buckling; later the leaves came which helped plants master photosynthesis. Plants were now more versatile and adaptable and ready to outcompete the fungi. Fungi such as the Prototaxites also fell prey to evolving insects which had begun to feed off of them!
Nevertheless, fungus is a fascinating organism unlike any known plant or animal. It is an outlier of sorts and has been accorded its own taxonomic animal kingdom. Fungi have crucially influenced the evolution of plants and animals, their diversity, their anatomical design and physiology. If it weren’t for the fascinating properties of the fungi, the world as we know it would cease to exist. Fungi play the crucial role of decomposers, feeding on dead organic matter and releasing the nutrients back into the soil keeping the nutrient cycle circulating. We have only recently learnt of the incredible world of underground mycorrhizal fungi that not only help plant roots to absorb important minerals and nutrients in exchange for sugars from the photosynthesising plants, but also help the trees communicate with each other over a sophisticated roots-mycorrhizal fungi network through chemicals and exchange of nutrients! That is how trees in a forest “talk” to each other and function as a cohesive unit.
More recently in history, we humans, have benefitted quite hugely from the fungi. Think of the fungus called Penicillium from which we extract the antibiotic penicillin that saves millions of lives every year. Think yeast and its fermenting ability that gives us our favourite alcoholic beverage – beer, and of course bread, that sustained civilisations!
As per recent estimates, an astounding 5.1 million fungal species are believed to reside on this planet. And we have barely discovered about one per cent of them! Fungi are everywhere. Even on us, inside us. Fungi that help us and those that make us sick.
There is so much more to fungi than what meets a human eye!
About the author: Purva Variyar is a conservationist, science communicator and conservation writer. She works with the Wildlife Conservation Trust and has previously worked with Sanctuary Nature Foundation and The Gerry Martin Project.
Disclaimer: The author is associated with Wildlife Conservation Trust. The views and opinions expressed in the article are her own and do not necessarily reflect the views and opinions of Wildlife Conservation Trust.
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