Fundamental fungi: the forgotten kingdom vital to our future

At the end of 1993 the Convention on Biological Diversity came into force. A key piece of global legislation in the promotion of sustainable development, it marked a change in focus for environmental concerns. Whereas previous high-profile conservation efforts such as those of the World Wide Fund for Nature or Greenpeace were frequently aimed at individual species or regional ecosystems, the legislation initiated by the 1992 Earth Summit in Rio de Janeiro was aimed at the biota of the entire planet. However, there are still segments of enormous ecological importance that are lacking sufficient research.

I've previously discussed how little attention general-readership natural history pays to the kingdom of fungi, which may have somewhere between 1.5 million and 3.8 million species. Of these, less than 150,000 have been scientifically described. Clearly, this is one life form where our knowledge barely covers the tip of the iceberg. It's hardly as if this attitude is a new one, either. While Linnaeus produced comprehensive editions on plant and animal taxonomy in the 1750s, it took over seventy years for anyone to bother with fungi: it wasn't until 1821 that another Swedish naturalist, Elias Magnus Fries, produced an equivalent work called Systema Mycologicum.

Thanks to the majority of fungal material living either underground or in dark, damp environments such as leaf litter, the kingdom fails to get the attention it deserves. Even the forms we see more regularly, such as mushrooms and symbiotic lichen, engender little interest. Many people no doubt still mistake the former as plants - and are scared off any interest in the wild forms due to the dangers of poisonous species - while the latter are rarer in polluted, i.e. urban, environments and fail to compete in sight and scent with the glories of the flowering plants.

In the eight years since I wrote about the lack of interest in fungi, I've found reason to mention the long-forgotten kingdom in various important contexts. For a start, numerous animals and plants are becoming critically endangered due to fungal pathogens accidentally being spread by global travel. In addition, research over the past three years has shown that Aspergillus tubingensis and several other types of fungi show promise as a bio-friendly solution to plastic waste. Finally, last month I looked at non-animal protein substitutes, including the mycoprotein-derived Quorn.

Despite the potential of these various forms of fungi, the organism's losses due to rapid environmental changes don't appear to be garnering much attention. The IUCN Red List, which tabulates the differing levels of threat faced by all life on Earth, only shows 343 fungi as currently endangered; this contrasts with over 43,000 plants and 76,000 animals on the list. Undoubtedly, the Kingdom Fungi is being given an underwhelming amount of attention just as we are discovering how important it is to maintaining ecosystem stability and for the future of our species.

Recently published reports of studies conducted in the Amazon region show that deforestation has a long-term impact on soil biota, which in turn affects the entire local ecology. Studies of a range of habitats, such as primary forest, agricultural land (including monoculture), pasture/grazing, forestry plantations and secondary/regenerated forest showed that although overall fungal mass might remain consistent, species diversity is far lower outside of the original rainforest. The lack of fungal variety was linked directly to the lack of plant diversity in those biomes, with recovery a slow or unlikely prospect due to the newly-fragmented nature of the landscape preventing efficient dispersal of fungal spores.

There are some obvious points that agribusiness seems to ignore, such as the effects of pesticides and fertilisers on local fungi and the loss of microhabitats vital to maintaining a healthy variety of fungal species. If only more generalist fungi can survive the change in land use from the wonderful diversity of the rainforest (with up to 400 fungal species per teaspoonful) then this may have repercussions for future farming. As an example, the fungus Fusarium oxysporum has a phytopathogenic effect on agricultural plants including palm oil, but without competition from a wider cross-section of fungi (for example, Paraconiothyrium variabile) it could spread rapidly within a dismal monoculture environment. 

As a predominantly visual species, we humans are unthinkingly biased about the natural world based upon what we see: think cute giant panda versus the unappealing aesthetics of the blobfish. It really is a case of out of sight, out of mind, but unfortunately no amount of spin doctoring will make fungi as much loved as furry mammals. Yet our attitudes need to change if we are to maintain the delicate ecological balance; fungi are highly important for recycling nutrients, regulating carbon dioxide levels, and as a source of food and pharmaceuticals. Yet they remain the soil equivalents of the ubiquitous underwater copepods, unsung heroes of the global ecosystem. It's about time we took a lot more notice of this forgotten kingdom.

Valuing the velvet worm: noticing the most inconspicuous of species

Most of the recent television documentaries or books I've encountered that discuss extra-terrestrial life include some description of the weirder species we share our own planet with. Lumped together under the term 'extremophiles' these organisms appear to thrive in environments hostile to most other life forms, from the coolant ponds of nuclear reactors to the boiling volcanic vents of the deep ocean floor.

Although this has rightly gained attention for these often wonderfully-named species (from snottites to tardigrades) there are numerous other lifeforms scarcely noticed by anyone other than a few specialists, quietly going about their unassuming business. However, they may provide a few useful lessons for all of us, including that we should acknowledge there may be unrecognised problems generated when we make rapid yet radical modifications to local environments.

There is a small, unassuming type of creature alive today that differs little from a marine animal present in the Middle Cambrian period around five hundred million years ago. I first read about onychophorans in Stephen Jay Gould's 1989 exposition on the Burgess Shale, Wonderful Life, and although those fossil marine lobopodians are not definitively onychophorans they are presumed to be ancestral. More commonly known by one genus, peripatus, or even more colloquially as velvet worms, there are at least several hundred species around today, possibly many more. The velvet component of their name is due to their texture, but they bear more resemblance to caterpillars than to worms. They are often described as the ‘missing link' between arthropods and worms but as is usually the case this is a wildly inappropriate term in this context of biological classification. The key difference to the Burgess Shale specimens is that today's velvet worms are fully terrestrial: there are no known marine or freshwater species.

Primarily resident in the southern hemisphere, the largely nocturnal peripatus shun bright light and requiring humid conditions to survive. Although there are about thirty species here in New Zealand, a combination of their small size (under 60mm long) and loss of habitat means they are rarely seen. The introduction of predators such as hedgehogs - who of course never meet peripatus in their northern hemisphere home territory - means that New Zealand's species have even more to contend with. Although I frequently (very carefully) look under leaf litter and inside damp logs on bush walks in regions known to contain the genus Peripatoides - and indeed where others have told me they have seen them - I have yet to encounter a single specimen.

There appears to be quite limited research, with less than a third of New Zealand species fully described. However, enough is known about two species to identify their population status as 'vulnerable'. One forest in the South Island has been labelled an 'Area of Significant Conservation Value' thanks to its population of peripatus, with the Department of Conservation relocating specimens prior to road development. Clearly, they had better luck locating velvet worms than I have had! It isn't just the New Zealand that lacks knowledge of home-grown onychophorans either: in the past two decades Australian researchers have increased the number of their known species from just seven to about sixty.

Their uncanny resemblance to the Burgess Shale specimens, despite their transition from marine to terrestrial environments, has led velvet worms to be described by another well-worn phrase, 'living fossils'. However, is this short-hand in any way useful, or is it a lazy and largely inaccurate term? The recent growth in sophisticated DNA analysis suggests that even when outward anatomy may be change little, the genome itself may vary widely. Obviously DNA doesn't preserve in fossils and so any such changes cannot be tracked from the Cambrian specimens, but the genetic variation found in other types of organisms sharing a similar appearance shows that reliance on just external anatomy can be deceptive.

Due to lack of funding, basic taxonomic research, the bedrock for cladistics, is sadly lacking. In the case of New Zealand, some of the shortfall has been made up for by dedicated amateurs, but there are few new taxonomists learning the skills to continue this work - which is often seen as dull and plodding compared to the excitement of, for example, genetics. Most people might say so what interest could there be in such tiny, insignificant creatures as peripatus? After all, how likely would you be to move an ant's nest in your garden before undertaking some re-landscaping? But as shown by the changing terminology from 'food chains' to 'food webs', in most cases we still don't understand how the removal of one species might generate a domino effect on a local ecosystem.

I've previously discussed the over-reliance on 'poster' species such as giant pandas for environmental campaigns, but mere aesthetics don't equate to importance, either for us or ecology as a whole. It is becoming increasingly clear that by weight the majority of our planet's biomass is microbial. Then come the insects, with the beetles prominent both by number of species and individuals. Us large mammals are really just the icing on the cake and certainly when it comes to Homo sapiens, the rest of the biosphere would probably be far better off without us, domesticated species aside.

It would be nice to value organisms for themselves, but unfortunately our market economies require the smell of profit before they will lift a finger. Therefore if their usefulness could be ascertained, it might help generate greater financial incentive to support the wider environment. Onychophorans may seem dull, but there are several aspects to them that is both interesting in itself and might also provide something fruitful for us humans.

Firstly, they have an unusual weapon in the form of a mechanism that shoots adhesive slime at prey. Like spider silk, is it possible that this might prove an interesting line of research in the materials or pharmaceutical industries? After all, it was the prickly burrs of certain plants that inspired the development of Velcro, whilst current studies of tardigrades (the tiny 'water bears' living amongst the mosses) are investigating their near indestructability. If even a single, tiny species becomes extinct, that genome is generally lost forever: who knows what insights it might have led to? Although museum collections can be useful, DNA does decay and contamination leads to immense complexities in unravelling the original organism's genome. All in all, it's much better to have a living population to work on than rely on what can be pieced together post-extinction.

In addition, for such tiny creatures, velvet worms have developed complex social structures; is it possible that analysis of their brains might be useful in computing or artificial intelligence? Of course it is unlikely - and extinction is nothing if not natural - but the current rate is far greater than it has been outside of mass extinctions. Losing a large and obvious species such as the Yangtze River dolphin (and that was despite it being labelled a ‘national treasure') is one thing, but how many small, barely-known plants and animals are going the same way without anyone noticing? Could it be that right now some minute, unassuming critter is dying out and that we will only find out too late that it was a vital predator of crop-eating pests like snails or disease vectors such as cockroaches?

It has been said that ignorance is bliss, but with so many humans needing to be fed, watered and treated for illness, now more than ever we need as much help as we can get. Having access to the complex ready-made biochemistry of a unique genome is surely easier than attempting to synthesise one from scratch or recover it from a long-dead preserved specimen? By paying minimal attention to the smallest organisms that lie all around us, we could be losing so much more than just an unobtrusive plant, animal or fungus.

We can't save every species on the current endangered list but more attention could be given to the myriad of life forms that get side-lined by the cute and cuddly flagship species, usually large animals. Most of us would be upset by the disappearance of the eighteen hundred or so giant pandas still left in the wild, but somehow I doubt their loss would have as great an impact on the surrounding ecosystem than that of some far less well known flora or fauna. If you think that's nonsense, then consider the vital roles that bees and dung beetles play in helping human agriculture.

Although the decimation of native New Zealand wildlife has led to protective legislation for all our vertebrates and a few famous invertebrates such as giant weta, the vast majority of other species are still left to their own devices. That's not to say that the ecosystems in most other countries are given far less support, of course. But without funding for basic description and taxonomy, who knows what is even out there, never mind whether it might be important to humanity? Could it be that here is a new field for citizen scientists to move into?

Needless to say, the drier climes brought on by rising temperatures will not do peripatus any favours, thanks to its need to remain in damp conditions. Whether by widespread use of the poison 1080 (in the bid to create a pest-free New Zealand by 2050) or the accidental importation of a non-native fungus such as those decimating amphibians worldwide and causing kauri dieback in New Zealand, there are plenty of ways that humans could unwittingly wipe out velvet worms, etal. So next time you watch a documentary on the demise of large, familiar mammals, why not spare a thought for all those wee critters hiding in the bush, going about their business and trying to avoid all the pitfalls us humans have unthinkingly laid for them?