Spore dispersal in fungi is diverse, but the majority of species utilize wind dispersal. Unlike the bulk of plant seeds (pun intended), spores are far lighter in weight, so their spores can traverse far greater distances. This spore quality helps us understand why so many species of fungi utilize wind dispersal. Even still, other dispersal strategies have evolved over and over again. Take the truffles for example. The pungent compounds these belowground fungi produce is irresistible to us hairy, extremely active and hungry animals, so we readily seek them out for consumption. Forest dwelling non-human mammals then defecate the consumed truffle spores-thereby dispersing them to other parts of the forest in nitrogen rich poop. Like the variety of truffle species that utilize mammalian dispersal, the fungus featured today has evolved a similar, but uniquely different dispersal strategy worth learning about. This exceptional fungus is completely new to me, and grows remotely on pretty much the opposite side of the world only in Australia and New Zealand. I have admiration for this species, because I realize that if I ever want to truly see this species in person I will have to fly the longest flight possible from my current location. Its unique dispersal ecology, as well as its isolated occurrence in two most distant places has persuaded me to enter Leratiomyces erythrocephalus on my bucket list.
Leratiomyces erythrocephalus is more commonly known as the red pouch fungus. At a first glance, the mushroom looks like a stalked puffball. Now puffball morphology has evolved independently several times over, so by calling a species a puffball, you are not referring to its ancestral lineage, but just the current traits their fruiting bodies possess. Although it may look like a stalked puffball, Leratiomyces erythrocephalus doesn’t release clouds of spores when animals or raindrops tap its spherical cap structure. Instead, this fungus, like the truffles, entices animals to consume them for their dispersal. Only, instead of creating pungent aromas to be located, the fungus visually attracts its main disperser.
Based on an animal’s ecology and physiology, some may depend on specific senses to find a food source. Mammals have keen noses, and relatively poor eyesight, while birds depend more on their amazing eyesight to locate food. In fact, relative to their body size, birds have the largest eyes compared to the rest of the animal kingdom. Birds hundreds of feet up in the air can’t smell potential prey from those distances so the selection towards higher functioning eyes is easy to grasp. Contrasting human eyes with a measly 200,000 photoreceptors per mm2, the number of photoreceptors in bird’s eye can be in the millions per mm2! Additionally, in diurnal birds (active during the day), up to 90% of these receptors may be color grasping cones. For these reasons, birds can see the color red exceedingly well.
Plants that have co-evolved with birds for millennia utilize the color red, because their avian counterpart can see it so well. Plants adapted for bird pollination produce red flowers, plants adapted for bird dispersal produce red fruits. It is as simple as that. Here is where Leratiomyces erythrocephalus comes in though. These fungi actually mimic red fruits that evolved to utilize bird dispersers. By looking so similar to small red fruits, these fungi also get dispersed extremely far by birds, and have the edge over wind dispersed spores, since they have access to rare nitrogenous resources in the form of bird poop.
Using animal dispersers definitely has its perks. For one, spores and seeds can get dispersed really far depending on which animal consumed them. Secondly, nutritious fecal matter kickstarts seed and spore germination, and aids the juveniles in their most vulnerable stage. Thirdly, since animals require water as well, seeds and spores are for the most part dispersed in less random fashion, closer to water resources. Compared to wind dispersed spores, fungal spores dispersed by mammals and birds land in a more suitable location, with a supply of available nutrients. It is rather fitting that this species is native to New Zealand where there are no native terrestrial mammals. New Zealand does have native bat species, and marine mammals, but no soil dwelling mammals that would otherwise have a large selection pressure on the fungal assemblages. Instead, species here depend more on bird dispersal.
Leratiomyces erythrocephalus is from the Strophariaceae, a common family of gilled mushrooms. Genomic analysis has revealed that this species is relatively new to Earth’s scene. Although they are closely related, it differs from its gilled ancestors that depend on wind both ecologically and morphologically. Unlike the revealed gills in its closely related cousins and ancestors, Leratiomyces erythrocephalus has an enclosed cap morphology that keeps spores within the fungal structure until consumption. This recent evolutionary development has its similarities and differences with truffle fungi too. Yes, they both entice animals to disperse them, but Leratiomyces erythrocephalus does it visually, tapping in to the amazing eyesight of birds, while truffles tap in to the nostrils and (let’s face it) taste buds of their mammalian counterpart. This just goes to show you how huge of a role the animal kingdom has in ecosystems around the world.