Rainforest

Mmm..biodivers-o-licious

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Adventures of a clumsy National Geographic Explorer person in Far North Queensland (Part 3): Can we eat it?

The rainforest is full of a dazzling array of forests fruits and seeds. Through the course of this research my team and I have collected, collated, identified and cleaned many, many seeds much to the amusement of folks that share our accommodation space. The fascination with rainforest seeds seems to be shared by many people and while we work de-fleshing and de-maggotting seeds, we receive questions, and comments in question form, from curious by-standers. “Is that bush tucker”, “Is that edible”, “Have you eaten that”, “That smells like a plum”, “They look like olives”. I think these questions are quite revealing of the human-centric way we interpret our world as they can all be pretty well summed up in one question: “Can I eat that?”

From front going clockwise: brown seeds with dark red of Myristica insipida (native nutmeg); ‘sweet-potato chip’ seeds of Cardwellia sublimus, blue pune-sized seeds of Endiandra Sankiana (a laural); small purple seeds of Litsea leefeana (also a laural); red seeds of a podocarp (a species of conifer); Plum sized seeds of Crysophyllum sp.; olive-sized seeds of Cryptocaryra angulata (yet and other laural), pod full of winged seeds of a Lomatia tree; Mahogony coloured seeds of Garcinia endophloem (a member of the mangosteen family).

The answer to that question?

No.

No, you cannot because these are my research and we’ve spent many days collecting them.

No, you cannot because I am not a “Dr of Bush Tucker” (although I wish I knew about that sort of thing)

And No, you cannot because while I don’t know if this fruit is edible, I do know that 80 % of the fruits in the Australian rainforest are poisonous.

But there’s so many more interesting things to know about seeds beyond whether or not you can eat them. We might ask: “what’s the reason for the wide variety of colour and form?” or we might ask “who eats them?”. Sometimes these questions are intimately entwined.

Colour, nutrition and a trick of the light:

Many seeds cloak themselves in colour to attract seed disperses. Red is quite popular being particularity attractive to birds. The seeds of the native nutmeg, Myristica insipida, have an underwhelming brown-yellow casing but the seed itself is wrapped in deep red, highly nutritious, aril (below left). The aril attracts disperses and can also be dried and powdered to produce mace.

In contrast, the enigmatic elocarpus or blue quandong seed (right; photo from Harms & Green, 2014) are blue to a point where they are iridescent yet the skin of these friut does not contain much in the way of nutritional value. Nor does it contain a single molecule of blue pigment!

The Pollia condensata fruit from Africa performs that same trick, an eye-catching iridescent blue, more intense than that of any previously described biological material, created without the aid of blue pigment (seriously click the link it’s a beautiful fruit).

What is actually occurring on the skin of these seeds is a complex bending and refracting of white light to create blue iridescence. This is achieved by taking lines of cellulose (the basic building block of all plant matter) called microfibrils and arranging these lines side-by-side into planes. The planes of microfibrils are then in turn arranged in helicoid stacks. The complex architecture refracts light creating an intensely iridescent blue. This is much the same process that creates the iridescence seen in the blue wing of the Papilo ulessus butterfly which gently drifts through the canopy above us as we work. It seems like a complicated process just to make blue, but the aim of these seeds is to trick seed disperses (birds and critters) into taking the seed for little or no nutritional return. To pull off such a trick I guess you need to be a pretty special looking blue.

Dispersal strategy and staying power

In the rainforest a plant faces an interesting conundrum when it come to the choice of seed that it creates. We know that seeds that disperse farther away from their parent tree, and their brother and sister seedlings, tend to have a better chance of surviving (see post 2) so there is an advantage to having a guaranteed dispersal strategy. This is exactly what winged seeds do. They use the wind to carry seeds far from the parent tree. In the image at the top of this post there are two winged seed morphologies. The flaky brown seeds, which an onlooker quite astutely described as ‘sweet-potato chip’ seeds, see-saw clumsily down to the forest floor. These are the seeds of Cardwellia sublimus.  The pod full of winged seeds with yellow dust over the seed (it’s not pollen) fly like helicopters through the under-story. These are the seeds of a Lomatia tree.

There are many tree species with winged seeds in rainforests, but by and large rainforest seeds take the form of large fleshy fruits, many of which contain one seed per fruit.  When these seeds leave the mamma tree, their nursery ground immediately rises to meet them with a resounding ‘thunk’. That is, they pretty much fall straight down. They might roll down the hill a bit if the parent tree is growing on a steep enough slope. But largely there is not much dispersal happening during the journey from canopy to ground. So why are so many rainforest tree species sacrificing their dispersal ability in favour of these mighty conkers? It seems like a lot of energy must go into making such large seeds. And there’s the answers. Energy. When you cut open one of these seeds, you’ll find two large fleshy halves. These are actually the seeds first leaves. They look nothing like any of the leaves that will follow, they are not true leaves, they have special name ‘cotyledons’ and they are energy reserves.

Cotyledons of a winged seed are thin and designed to photosynthesize (above left); Golf-ball sized fleshy cotyledons from large seeds remain at the base of the seedling with a very minimal for photosynthesis (green area).

The cotyledons of winged species are thin, emerge and disappear quickly and are almost entirely used for harvesting light into energy. In contrast the cotyledons of large-seeded species hang around for a long time but contribute little towards photosynthesis – some even stay encased in their seed coat. These cotyledons are energy reserves. The idea is that in a rainforest for a seedling to survive and become a tree it needs to persist for a long time. It needs to persists even though there is extremely low light, it needs to persist even if leaf litter covers its photosynthetic leaves and it needs to persists -and re-sprout – if its shoot gets eaten. It may need to wait a very long time because things the rainforest under-story happen sloooowly, so having a storage reserve confers a selective advantage (Green and Juniper, 2004).

‘How slow?’ I hear you ask. Well, for more then 50 years ecologists have painstakingly tracked the growth of thousands of seedlings, sapling and trees at Davies Creek: in that 50 years some plant have only grown few feet (Harms and Green, 2014).

So it seems survival in the dark is the order of the day for rainforest seedlings and large seeds which come with a packed lunch of energy reserves are one way to help the seed manage this suppressive environment. In terms of dispersal – not all is lost – these seeds simply outsource the job. The fleshy, and often fragrant, outer coverings of the fruit attract cassowaries and other native animals such as the white tail rat which will redistribute the seeds around the forest. The rats create caches of seeds that if forgotten long enough will germinate, and cassowaries leave steaming seed patties in the wake of their wanderings.  Dispersing seeds, encouraging diversity and making seed collection for this ecologist as simple as poo-pie.

Ask not: Can you eat that seed? | Ask: What can that seed tell you?

Dr Jen Wood
@JW_ilikedirt

All thoughts and photos by Jen Wood unless otherwise indicated

Green, P.T. and Juniper, P.A. (2004). “Seed–seedling allometry in tropical rain forest trees: Seed mass-related patterns of resource allocation and the ‘reserve effect’.” Journal of Ecology 92(3): 397-408.

Harms, K.E. and Green, P. T. (2014). “Under the lunch tree: 50 years of rainforest dynamics in Queensland, Australia.” Natural History March 2014

The mystery of the rainforest

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Adventures of a clumsy National Geographic Explorer person in Far North Queensland (Part 2): Why are rainforests so diverse?

If you know one thing about rainforests, it’s probably that you know they are diverse. You’d be right. But do you know why they are so diverse?

Less than 1 square kilometer of rainforest can harbour more plant diversity than one million square kilometers of temperate forest (Wright 2002, Wood et al. 2019).

That’s really diverse. But, why are rainforests so diverse?

The answer is simple: we don’t know.

As far as ecosystems go, rainforests are uncommon. Most forest ecosystems around the world typically have only a few dominate canopy species: Conifer forests are monodominant (only have one dominate species); southern Australian bushland will typically have two maybe three dominant canopy species (for example a eucalypt and one or two acacia species).  In contrast, just one hectare of rainforest can harbour up to 100 different species of canopy tree, all jostling for light but equally finding space.

Not just a sea of green: look closely at a rainforest canopy and you will see a wide variety of colour (albeit green colours), form, and shape.

The immense plant and animal diversity rainforests harbour provide crucial ecosystem services (air and water filtering, climate regulation etc.), attract economic benefits though ecotourism (Prideaux 2014) and  continue to contribute to the discovery of new therapeutics (Balunas and Kinghorn 2005, Perigo et al. 2016) and novel species (Jay et al. 2016, McDonald et al. 2016). Clearly rainforest diversity is important – we’ve known this for a long time – so how is it we still don’t understand what makes rainforests so diverse?

Part of the puzzle is that in the rainforest some tree species are prolific seed producers, while other species are far less prolific. Why then, don’t the prolific seed producers come to dominant the canopy? Or at least, why don’t we see dense stands of one tree species within the rainforest – localized dominance if you will?*

Actually we do see dense assembles of one plant species, when we look among the seedlings, but something happens between seedling and mature rainforest that thins the herd and results in an increase in diversity. In the 1970s two ecologists working independently, Daniel Janzen and Joe Connell (who established and was working on the same field site we are using today), realised that diversity could be maintained if there were some mechanism that stopped common species from growing and coming to dominate whilst allowing rarer species to grow unchecked. A balancing effect that evens the odds among tree species within the community. We refer to this ‘force’ as non-random mortality (because it non-randomly kills off common species but not the rare species) and it has become the cornerstone rainforest diversity research and is encapsulated in what is now known the Janzen-Connell hypothesis.

*localized dominance is actually a thing that happens in rainforests, but not often, and its an area of research interest in its own right.

Who or what is causing non-random mortality in rainforests?

Countless studies have tried to understand patterns of non-random mortality in rainforests. Whilst  vertebrate seed/seedling-predators (Theimer et al. 2011, Kurten and Carson 2015) and insects (Swamy and Terborgh 2010, Bagchi et al. 2014) have been proposed as the cause of non-random seedling mortality, by far the most convincing body of evidence implicates soil-microbial pathogens (Augspurger 1983, Augspurger and Kelly 1984, Gilbert et al. 1994, Bell et al. 2006, Bagchi, Gallery et al. 2014). Which brings me to why we are here doing research supported by the National Geographic Society. Whilst microbes have been inferred as the cause of non-random mortality, very few studies have dug that bit deeper (pun intended) to investigate what make these soil communities tick. Our research aims to look at these rainforest soil microbial communities and see what they are doing.

So how do tiny microbes shape entire ecosystems?

Non-random mortality seems to be related to one of two things: the distance of a seedling from the mamma tree (this is distance dependent mortality) or the density of the seedling patch (density-dependent mortality). The idea behind microbial distance-dependent mortality is that many prolific seed producers create large seeds that fall straight down. If the parent tree harbors a host-specific pathogen reservoir in their root-zone then seedlings germinating close to their parent-tree are more exposed to pathogen attack than a seedling that germinates farther away. In this way the seedling from prolific seed producers are rapidly thinned. Microbial density-dependent mortality is thought to occur due to locally abundant seedlings (i.e. seedlings germinating in dense assemblages) attracting a higher pathogen load than rarer seedlings that germinate in isolation.

That’s some pretty heavy science thoughts. But the key points are we think soil microbes can create rainforest diversity, quite literally, from the ground up. If we can understand how they do this – and what they need to do this – then our odds of conserving these biodiversity hot spots in the face of a changing climate will dramatically increase.

Rainforest biodiversity. It’s a thing.

Rainforest biodiversity| so important | still a mystery |maybe microbes hold the key

Dr Jen Wood
@JW_ilikedirt

Augspurger, C. K. (1983). “Seed dispersal of the tropical tree, platypodium elegans, and the escape of its seedlings from fungal pathogens.” Journal of Ecology 71(3): 759-771.

Augspurger, C. K. and C. K. Kelly (1984). “Pathogen mortality of tropical tree seedlings: Experimental studies of the effects of dispersal distance, seedling density, and light conditions.” Oecologia 61(2): 211-217.

Bagchi, R., R. E. Gallery, S. Gripenberg, S. J. Gurr, L. Narayan, C. E. Addis, . . . O. T. Lewis (2014). “Pathogens and insect herbivores drive rainforest plant diversity and composition.” Nature 506(7486): 85-88.

Balunas, M. J. and A. D. Kinghorn (2005). “Drug discovery from medicinal plants.” Life Sciences 78(5): 431-441.

Bell, T., R. P. Freckleton and O. T. Lewis (2006). “Plant pathogens drive density-dependent seedling mortality in a tropical tree.” Ecology Letters 9(5): 569-574.

Gilbert, G. S., R. B. Foster and S. P. Hubbell (1994). “Density and distance-to-adult effects of a canker disease of trees in a moist tropical forest.” Oecologia 98(1): 100-108.

Jay, K. R., Z. R. Popkin-Hall, M. J. Coblens, J. T. Oberski, P. P. Sharma and S. L. Boyer (2016). “New species of austropurcellia, cryptic short-range endemic mite harvestmen (arachnida, opiliones, cyphophthalmi) from australia’s wet tropics biodiversity hotspot.” ZooKeys 2016(586): 37-93.

Kurten, E. L. and W. P. Carson (2015). “Do ground-dwelling vertebrates promote diversity in a neotropical forest? Results from a long-term exclosure experiment.” BioScience 65(9): 862-870.

McDonald, K. R., J. J. L. Rowley, S. J. Richards and G. J. Frankham (2016). “A new species of treefrog (litoria) from cape york peninsula, australia.” Zootaxa 4171(1): 153-169.

Perigo, C. V., R. B. Torres, L. C. Bernacci, E. F. Guimarães, L. L. Haber, R. Facanali, . . . M. O. M. Marques (2016). “The chemical composition and antibacterial activity of eleven piper species from distinct rainforest areas in southeastern brazil.” Industrial Crops and Products 94: 528-539.

Prideaux, B. (2014). Rainforest tourism, conservation and management: Challenges for sustainable development.

Swamy, V. and J. W. Terborgh (2010). “Distance-responsive natural enemies strongly influence seedling establishment patterns of multiple species in an amazonian rain forest.” Journal of Ecology 98(5): 1096-1107.

Theimer, T. C., C. A. Gehring, P. T. Green and J. H. Connell (2011). “Terrestrial vertebrates alter seedling composition and richness but not diversity in an australian tropical rain forest.” Ecology 92(8): 1637-1647.

Wood, J. L., P. T. Green, J. J. Vido, C. Celestina, K. E. Harms and A. E. Franks (2019). “Microbial communities associated with distance- and density-dependent seedling mortality in a tropical rainforest.” Plant Ecology.

Wright, S. J. (2002). “Plant diversity in tropical forests: A review of mechanisms of species coexistence.” Oecologia 130(1): 1-14.

All thoughts and photos by Jen Wood unless otherwise indicated

Flamin’ biodiversity

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Adventures of a clumsy National Geographic Explorer person in Far North Queensland (Part 1): Access denied

It’s day one of field work. We are cruising along a dirt road in Davies Creek National Park en route to our field site deep within the rainforest that constitutes the Eastern half of the park. We drive through a landscape of lemon-scented gums dotted with flowering grass trees, then into spindly casuarina forests which give way briefly to towering stands of eucalyptus grandii before plunging into pristine rainfor– … a road closed sign?!

Clearly, we didn’t literally plunge into the road closed sign. But blocking the road to our field site and all the work we had planned to do sat a simple, obstinate sign reading ‘Entry prohibited’.  Bugger.

Photo credit: Josh Vido, Research associate

The road to our field site, the Davies Creek long-term rainforest plot, is closed because there is an active bush fire. At this point, I am thinking back to doing the risk assessment for this trip and recall getting to the ‘risk of bush fire’ section and thinking ‘lol, rainforests don’t burn’. Yet here we are.   

Fire is a part of the Australian landscape and integral to the ecology of many of our ecosystems. Many species are fire adapted to the point that fire is necessary for their survival: the giant mountain ash forests of southern Australia are re-invigorated with new life. After fire passes through, swallowing the adult trees, the accumulated seed bank, which may not have germinated for several decades, springs to life creating a new stand of mountain ash. This explains why the ghostly trunks of mountain ash all adhere to a regulation size which makes these forest so enigmatic. Many species of acacia have a similar life strategy and if you happen upon a stand of acacia all of the same apparent age, a savvy ecologist can estimate the time since the last fire passed through. The pods of banksia species remain on the tree, clamped tightly shut with the next generation of seeds safely locked inside until the heat from a passing bush fire causes them to snap open, spraying the ground with fresh seeds ready to germinate in the now competition-free landscape (Huss et al. 2019). This phenomenon is called serotiny. The list trees species in Australia with adaptations to survive and work in concert with bush fire goes on. This makes sense, unlike animals, trees can’t get out of the way of a fire so they need to find a way to work with it.

Above: White trunks of fire-adapted Mountain Ash from Otway National Park (left). Banksia pods in the Blue Mountains near Katoomba (right).

Looking around the charred remains of the landscape, while we wait for a ranger to arrive to confirm the whether the road to our study site is/is not closed, I am reminded that not all animals are made equal when is comes to escaping a fire. For example, what chance does a land-snail have? No legs, no wings, no burrow, no-where to go.

Above: the shells of native land snails litter the ground after a small grass fire has passed through Davies Creek National Park

Snails and other leaf-litter dwelling critters provide crucial ecosystem services, reincorporating carbon from leaf litter into the soil. Perhaps the best adaptation these animals have to cope with fire is to be most active when fire is least likely to occur: in winter or in the wet season (depending where you live in Australia). Microbes are among the list of critters integral to soils and soil function that are not going to be fleeing from fire. Whilst lower reaches of the soil may be buffered from the impact of burning, big fires, like the Black Saturday fires that decimated Marysville and King Lake in Victoria in 2009 burnt so hot that PVC piping buried 1 m below the ground, was found melted. Not much could have survived that. So how are soils recolonised after fire? Where does the new generation of microbes and other soil-dwelling critters come from? How long does it take to rebuild these communities?.

Above: Images King Lake National Park landscape recovering from the 2009 bush fires, taken in 2012

Studies on this question may be particularly important when thinking about fuel-reduction burning which typically occurs in winter when the ground is damp. While this is to be sure a safest time to burn-off leaf litter and ensure the fire will remain under control, this is also the time of year that soil microbes – and all the other soil-dwelling critters – are most active. So how is a soil community that gets burnt during summer, when insects and microbes have effectively shut up shop for the year, impacted by fire and is it different from how communities react to being brunt when they are in full swing, defenses down, during the wet? I suspect it matters a lot.

Rainforest soils provide and interesting tangent upon which to take these musings. Rainforests are not meant to burn. In fact, they are notoriously resistant to fire. But as the climate changes some rainforests are becoming dryer (others will become wetter) and they are starting to burn. This year fire brunt 440 ha of sub-tropical rainforest in Lamington national park. There are multiple lines of evidence to suggest that soil microbes have an important role to play in creating the impressive levels of diversity seen in rainforest plant communities. We don’t know exactly which microbes or microbial functions are key to creating plant diversity, but we do know that diversity plant-microbe interactions occur among seedling and small saplings (Green et al. 2014). Given that the entire ecosystem is not fire adapted, it seems likely (to me at least) that the microbes that carry out these processes will not be adapted to fire either. So when a rainforest burns, and it comes time for plants to regenerate and recolonize the space, will the diversity return to the rainforest or will disrupting processes in the soil have profound flow-on effects for the whole ecosystem? We’re optimistic that the research we are here to conduct will in part begin answering this very question. We’ll be looking at how drought impacts microbial soil-function and whether this has flow-on effects for plant-microbe interactions that govern rainforest diversity. Provided, of course, we are able to access our site.

A quick sat-phone call to the local ranger confirms that the road is indeed closed for today due to fire, but we’ll be right tomorrow to access our site. Have a day off.

Fire in Australian rainforests: ecosystems evolved without fire | How does brunt rainforest recover? | How does brunt rainforest microbiology recover?

Dr Jen Wood
@JW_ilikedirt

All thoughts and photos by Jen Wood unless otherwise indicated

Green, P. T., K. E. Harms and J. H. Connell (2014). “Nonrandom, diversifying processes are disproportionately strong in the smallest size classes of a tropical forest.” Proceedings of the National Academy of Sciences, USA 111(52): 18649-18654.

Huss, J. C., P. Fratzl, J. W. C. Dunlop, D. J. Merritt, B. P. Miller and M. Eder (2019). “Protecting offspring against fire: Lessons from banksia seed pods.” Frontiers in Plant Science 10(283).

White death from above

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Photo credits: all photos by Jen Wood unless otherwise indicated

Adventures of a clumsy person in far north Queensland (part 2): The white-death fungus

So, when I’m in the rainforest helping with surveys, I tend to spend most of my time looking down. This is partly because I’m on seedling survey duty – and down is where the seedlings are at – and partly because I really am quite clumsy, so I’m watching my footing. But mostly I am looking down because I’m constantly on the lookout for interesting mushrooms, fungi and other tiny critters

But, it turns out I should have been looking up.

IMG_3030

Yes, on the forest floor there is every sort of wood-rotting fungi and colorful mushroom but up in the canopy there’s a fungi that has a wonderfully sinister name and modus operandi. It’s called white death and it kills by touching. White death, also known by the somewhat less dramatic name ‘Clavulicium extendens sp. nov.’, doesn’t appear to be a pathogen in the sense that it can’t infiltrate and infect living tissue (Hood and Ramsden, 1999), instead it forms dense white mats of mycelia that gradually cover leaves and branches often smothering smaller trees and saplings (dark, right?).

One of the most interesting things about white death is how it gets around. It appears to be transferred from tree to tree by touch. When a twig covered with white death touches a new tree, the fungus create at attachment pad (see below, center) where the twig and tree contact, binding them together. From there it proceeds to slowly cover the new tree. If you spot an under-story tree with white death on it, look up and more often than not, high up in the canopy, you’ll see that the source of the white death is a twig that has broken away from a taller tree also covered in the fungus. In this way white death leap-frogs from tree to tree down to the forest floor. Interestingly it doesn’t seem to matter what species of tree the fungus comes in contact with. No one knows the true host-range of this fungus (Green, PT , pers comm ).

So what’s this fungi doing so far up in the canopy and how does it get there? One possibility is that its spores are wind dispersed up into the canopy. Another possibility is that it has an animal that carries it around. Why might I think this? Well typically white death only affects and kills off the tips of a branch – the twigs and leaves here are small enough to be smothered. If it came into contact with a thick branch or a tree trunk its growth probably wouldn’t impact the tree. Yet looking up into the canopy we noticed (at least once – see above, left) that the highest point of a white death infection was a broad flat branch, exactly where a bird might perch as it flits through the rainforest canopy. What a bird would be doing carrying around fungal spores on their body or in their feces is anyone’s guess, but other animals have been known to eat fungi and maybe the infected twigs lying on the ground are a source of protein for some bird. This is of course wild speculation.

White death fungi: talented disperser | spreads by touch | white creeping death

Dr Jen Wood
@JW_ilikedirt

Hood, IA and Ramsden, M (1999) Clavulicium extendens sp. nov (Corticiaceae), a Fungus Spreading on Twigs in Queensland Rainforests. Australian Systematic Botany 12, pp 101–107

Horse-hair fungi

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Adventures of a clumsy person in far north Queensland (part 1): Horse-hair fungi

When you survey trees in a rainforest (and you are accident prone) you learn to walk through dense foliage with one forearm in front of your face. Sometimes you emerge with a tangle of lawyer vine whips wrapped around your wrist (which is preferable to having them wrapped around your head) and sometimes you emerge with a fist-full of what looks to be thick, coarse black hair. It very much resembles horse hair but it does not belong to any animal. It’s actually a mushroom! The aptly named, and surprisingly interesting, horse-hair fungus (Marasmius spp.).

Mushrooms play an important part in a rainforests life cycle. They are needed to decompose fallen logs and leaf litter in order for nutrients to be returned to the ecosystem. In fact one of the main chemical building blocks of plants, known as lignin, is so structurally complex that it can only be broken down by special groups of fungi known as white rot fungi (Floudas et al. 2012). Most mushrooms are found on the forest floor, which makes sense as this is where fallen leaves and wood all wind up – So what is this horse-hair fungi doing creating tangles among the tree branches? And why does it look like hair when it is supposed to look like a mushroom?!

To answer the second question first: there is more to mushrooms than just mushrooms. Mushrooms have long had a mystical aura about them because the appear so suddenly after the rain and seem to disappear almost as quickly. But nothing appears from nothing. Mushrooms actually grow out of a vast network of near-microscopic roots called hyphae. The hyphae are present in the soil all year round, they can cover vast distances and be densely packed – 1 g of soil can contain as much as 3 km of fungal hyphae (Bardgett 2005)! Hyphae are the part of the fungus that interact with plant material and can decompose fallen logs and leaf litter; the mushrooms are really just the showy reproductive organs of the that grow out from the hyphal networks in much the same way a flower grows on a tree.

So, the hairs of the horse hair fungus are these hyphae. But instead of being super-fine and delicate, they are thick and coarse to avoid getting broken to pieces by wayward ecologists tumbling through the rainforest. If you come upon them at the right time of year you will indeed find mushrooms sprouting from these aerial hyphae.

But why aerial hyphae? What’s wrong with using the ground? There are many species of Marasmius mushroom and they all specialize in left litter decomposition. The tangled networks of aerial hyphae, produced by the horse-hair Marasmius, act as nets that catch and ensnare falling leaves before they reach the ground. This strategy means that horse-hair fungi don’t have to compete for food or real-estate on the forest floor where competition is pretty high. By settling among the trees these horse hair fungi can have a space all to themselves.

Having your own private food-larder away from other competitors is a pretty nifty trick, however some horse hair fungi have been reported to be a bit more proactive than this. Horse-hair fungi associated with tea-leaf bushes have been shown to release volatile compounds that actually cause the tea leaves to drop off into the fungi’s waiting hyphae (Su, Thseng et al. 2011, Aubrecht, Huber et al. 2013). Smart huh? That kind of smart doesn’t go unnoticed and it seems that horse-hair fungi has caught the eye of the local birds.

nest

When we found a nest in Far north Queensland that was lined with horse-hair fungi we thought that the birds had simply happened upon a nifty nesting material. But horse-hair fungi have shown up in nests all around the world and some researchers think that it may actually provide a benefit to the birds having water repellent properties (no one wants a soggy nest) and containing antimicrobial compounds that may help with nest hygiene (Aubrecht, Huber et al. 2013).

Horse hair fungi: loved by birds | a clever competitor | preferable to a face full lawyer vine

Dr Jen Wood
@JW_ilikedirt

Aubrecht, G., W. Huber and A. Weissenhofer (2013). “Coincidence or benefit? The use of Marasmius (horse-hair fungus) filaments in bird nests.” Avian Biology Research 6(1): 26-30.

Bardgett, R. D. (2005). The biology of soil : a community and ecosystem approach. New York, New York : Oxford University Press.

Floudas, D., Binder, M., Riley, R., Barry, K., Blanchette, R. A., Henrissat, B., . . . Hibbett, D. S. (2012). “The paleozoic origin of enzymatic lignin decomposition reconstructed from 31 fungal genomes.” Science 336(6089): 1715-1719.

Su, H. J., F. M. Thseng, J. S. Chen and W. H. Ko (2011). “Production of volatile substances by rhizomorphs of Marasmius crinisequi and its significance in nature.” Fungal Diversity 49: 199-202.

Photo credits: all photos by Jen Wood unless otherwise indicated