Out of all of the fungi that I’ve talked about here at Forest Floor Narrative, I realized today that I rarely mention any species of puffballs. I’m not being hard on myself, because again, this kingdom of organisms is about six times more diverse than that of the plants! With more than 5 million species of fungi filling nearly every ecological niche this planet has to offer, I can only really dive into a small subset of the diversity we see today. But even so, the puffballs are too interesting to leave out for this long. Today I present to you one of the coolest puffballs I have ever laid eyes on. Chlorogaster dipterocarpi.
It took me until now to recall my first experience with a fungus that wasn’t on my plate. As a young kid, my family and I were situated at a motel for a soccer tournament my older sister was in. Outside our room, a mossy tree stump lied. At the base of that tree, there was a cluster of small, brown puffballs, probably Lycoperdon pyriforme. Like any curious kid would, I touched the gasteroid fungus, and upon contact, a puff of cloud-like spores rushed out of the open pore at the top. I remember it so vividly, being mystified at this weird little brown thing.
Aptly named, the gasteroid species are made up of basidiomycete fungi that produce their spores within their fruiting bodies. Gastro is the Greek word for stomach, which specify where the spores of these fungi are formed. We all know that fungi don’t have stomachs, but by looking at their morphology and physiology the name starts making sense. Most other higher fungi produce their spores on their outer surfaces. When we look at all of the mushroom forming fungi, only 8.4% of them are represented by gasteroid taxa. Fungi that produce spores within their developing fruiting bodies include the puffballs as well as a family of fungi that gets a lot of attention on this blog, the Phallaceae, also known as the stinkhorns.
Like many fungal adaptations, this puffball-like lifestyle has evolved independently several times. So far, I have talked about how a polypore and a bolete have evolutionarily reverted back to a gilled morphology. Unlike these aforementioned mushrooms, a lineage that evolves a gasteroid ecology steps foot on a one-way road. When a species ‘figures out’ this gasteroid lifestyle, they lose the spore dispersal mechanism most species within the Basidiomycota have. Although boletes, gilled, and pored fungi may seem to have a passive spore dispersal mechanism by utilizing wind currents, their microscopic spores are released from basidia through an active mechanism (see figure below). When species traverse into the gasteroid realm, they lose these active mechanisms involving the Buller’s droplet. With this, we can see the unlikeliness that a species would revert back to a morphology with an active spore mechanism.
Puffballs depend on raindrops, falling debris or animals to come in contact with the mature fruiting bodies. When this happens, air within the fungus rushes out of the pore (or pores) at the top, thereby carrying millions of spores into air currents above the boundary layer hovering over the forest floor. These external stimuli are required by all puffballs, even the species featured in today’s post.
In 1999, an insanely cool species of puffball was found in Sabah forest located in Malaysia. After contacting tropical and gasteroid fungal experts to no avail, researchers Thomas Læssøe and Leo Jalink had found out that they had discovered a new species of fungus. By analyzing its morphological traits, Chlorogaster dipterocarpi, has been placed within the family Sclerodermataceae. Its fungal cousins include species of other hard-skinned puffballs, like Scleroderma citrinum, and Pisolithus tinctorius. The Sclerodermataceae is nested in the order Boletales, showing that its ancestors formed bolete-like mushrooms. Again, once its ancestors crossed this gasteroid plane, it was unable to revert back to its ancestral bolete condition.
Chlorogaster dipterocarpi is quite rare, and is thought to be ectomycorrhizal, once again revealing its bolete ancestry-with many of the boletes forming underground mutualisms with broadleaf trees. Not only is it a rare species, but its DNA is exceptionally difficult to isolate and sequence so its phylogeny to this day is still based on morphological traits. New, insanely cool species of fungi like this are found every year, which ultimately points to how much we don’t know about this incredible kingdom. We have only scratched the atomic surface of the fungal diversity within tropical rainforests, but this should be exiting news to the students of the forest floor. Species are just waiting to be discovered.