My little boy thinks fungi are really cool. I’m not sure if it’s because you can eat them, or because you can’t eat them (deadly poisons with no cure are worth paying attention to), or because they’re generally overlooked, or because, intrinsically, they’re really interesting. For the second year we joined the Adelaide Fungal Studies Group autumn excursion to Mount Lofty Botanic Garden led by Pam Catcheside. Pam is the acknowledged South Australian expert on toadstools and mushrooms and Honorary Research Associate at the State Herbarium. Pam is a mycologist – a ‘botanist’ who specialises in fungi, and particularly the taxonomy, distribution and ecology of macrofungi (aka toadstools and mushrooms).
I have to start by declaring (again if you recall February’s excursion on kelp), that botanists have disowned fungi as plants. Fungi belong to a separate Kingdom – the Eumycota or true fungi. Indeed, the origins of fungi suggest that fungi are more closely related to animals than to plants. Regardless, collections of toadstools and mushrooms continue to reside in herbaria and the mycologists that work with these collections are also unlikely to find a home elsewhere. The true fungi comprise a single, although extremely diverse, group of related organisms sharing a common ancestor (known as a monophyletic group). The presence of chitin (rather than cellulose) in fungal cell walls, together with the absence of chlorophyll, provides useful distinguishing characters between fungi and flowering plants. The toadstools and mushrooms we were looking for at Mount Lofty Botanic Garden are conspicuous in the right season and environment. However, fungi include a bewildering range of friends and foes ranging from microscopic species such as the famed Penicillium – source of the antibiotic penicillin, to macroscopic morels, truffles and field mushrooms as well as deadly poisonous species such as the Death Cap, Amanita phalloides. Fungi embrace hallucinogens, baker’s and brewer’s yeasts, plant diseases such as powdery mildew and wheat rust and human diseases such as ringworm and thrush.
Perhaps the most important fungi for life on Earth are usually overlooked. Fungi play a critical role in nutrient cycling by breaking down organic matter. Mycorrhizal fungi are also involved in nutrient cycling. These fungi form a mutualistic relationship with flowering plant roots – a relationship profoundly important for many or even most flowering plants. These processes provide the foundation for plant life, and, consequently, for our own. 2015 is the UN International Year of Soils – fungi are a major part of the story. The sheer scale of these processes is staggering. Pam outlined the importance of the role of fungi in, for example, decomposing wood. The Adelaide Fungal Studies Group continued the discussion by reflecting on the fundamental significance of this single example. The story of wood decomposition is a remarkable one that resonates today from events dating back 300 million years to the Carboniferous era.
Wood is comprised of cellulose and lignin. Cellulose is the most abundant natural polymer in the world and lignin the second most abundant. Cellulose and lignin work together to provide a structural function similar to glass fibres and epoxy resin in fibreglass. The fibrous cellulose (analogous to the glass fibres) provides the primary load-bearing elements while the matrix provided by lignin (analogous to the resin) provides stiffness and rigidity allowing trees to reach gargantuan proportions. Cellulose is relatively easy to break down. However, lignin remains astonishingly resistant to break down. Genomic analysis suggests white rot fungi capable of breaking down lignin only evolved within the last 300 million years. So why is this important? The whole of the Carboniferous period that saw the laying down of lignin and the formation of coal came to an end at the same time as fungi evolved the ability to break down lignin. The importance of fungi in the carbon cycle is vividly illustrated here, and the consequences for atmospheric carbon remain in play today.
The unsung but critical importance of fungi has been recognised and celebrated in some jurisdictions. In the USA, Oregon has designated brewer’s yeast (a fungus) as its state microbial emblem; Minnesota has the morel and Oregon the golden chanterelle as state fungal emblems. However, Australia is yet to establish a formal recognition of the value of fungi. Perhaps it’s time. Pam has suggested Cortinarius austrovenetus – a species described by legendary South Australian pathologist, State Coroner and naturalist Prof Sir John Burton Cleland in 1928. I’m inclined to support Pam’s proposal.
As State Coroner Cleland’s apocryphal words are often cited as a severe caution to eating wild fungi – he’s supposed to have said, “You can eat whatever you like but leave some for me”. In print his advice was more sanguine. In Toadstools and Mushrooms of South Australia Cleland notes,
“We may state here – and state emphatically – that there is no royal road for distinguishing edible from poisonous species”. Nationally the two authorities most likely to be contacted by poisons specialists following fungal poisonings are Dr Tom May and Dr Teresa Lebel at the Royal Botanic Gardens, Melbourne. Tom urges foragers to use great caution in eating wild fungi and advises, “When contemplating eating fungi, it is essential to identify them with certainty. Because there are many hundreds of species of mushrooms in Australian forests, confident identification is something that can only be done after an apprenticeship in the various characters that are required for identification.”
You might start that apprenticeship by joining the Adelaide Fungal Studies Group through the South Australian Field Naturalists Club (fnssa.org.au) and contribute to FungiMap (fungimap.org.au). Part of the excitement of working with fungi is that the field is still largely unexplored. If you’re reluctant to go into the field, at least visit the remarkable 19th century papier–mâché models in the Santos Museum of Economic Botany in Adelaide Botanic Gardens.
“We don’t scare easy. We’re Mycologists.”
“Yes, Fungi make you brave.”
Stephen Forbes, Director, Botanic Gardens of South Australia
Originally published in The Adelaide Review on 3 August 2015.