Earlier this week, a new time-lapse video has gone viral showing the fruiting and growth of several different species of fungi and slime molds. The thumbnail image is that of and an interesting Phallus species. Thumbnails are key tools used by content creators that, when used correctly, draw readers and viewers in. I just love it when fungi make it to mainstream media, so I was delighted to see that the video accrued more than 41 million views on Facebook! Across all of my social media accounts, friends, family and my connections in academia shared or tagged me in this video, because they thought it was cool, and thought I would appreciate it. They weren’t wrong! The video is eye-catching, but again, the thing that excites me most is the popularity of it. With no information regarding the fungi featured in the video, it still entices viewers to learn about these forest floor inhabitants. Content like this can be used to battle scientific illiteracy; which is my exact modus operandi.
With the thumbnail image drawing viewers in to this viral video, I thought I would relay some information about this stunner of a species. Compared to other fungi, Phallus indusiatus and other Phallus species produce a netted-looking veil that falls to the forest floor. This cascading structure makes this species one of the best subjects for time-lapse photography, but the main question is why does this structure exist in the first place? This structure does have fitness enhancing characteristics that many mycophiles don’t know about. In this edition of Fungi Friday, I will describe the ecology and different structures evolved in this charismatic species.
Over millions of years, natural selection has favored this net-like fungal veil, but to understand its function we need to quickly remind ourselves about the stinkhorn family it belongs to, the Phallaceae. Stinkhorns fruit from forest floors in temperate and tropical regions around the world. They’re extremely successful, much like the first flowering plants were. Like those first flowering plants, these fungi also attract insects. Stinkhorns, like their name suggests, produce a stinky, brown, spore filled mucous-like substance called gleba. In fact, two of the six times I’ve found stinkhorn species, I smelled the organism before visually locating it. Insects that normally eat and lay their larvae in dead animals (carrion) find gleba irresistible.
I truly believe that this family of fungi is going through a period of adaptive radiation. Instead of depending on wind dispersal, enticing flying insects is a great way to increase the chance of successful spore germination. Insects and fungi have similar resource requirements when it comes to water and temperature, so a gleba covered fly inevitably will land on a position of the forest floor where the spores can germinate. The insects don’t do this for free either, as some of the carbohydrate rich gleba becomes consumed. With a clear mutualism in place, the presence of both species will enhance their collective fitness. Over long enough time periods, specializations will certainly occur, and eventually new species will form. The rate of speciation within this stinkhorn family should be higher compared to other fungal families if my hypothesis is correct.
Realizing the ecology of stinkhorns, we can now begin to divulge the multiple function these netted veils possess. Like flower petals, these veils act as visual cues, advertising a potential meal for the flying insects above. Without these veils, fewer insects would be able to locate these fungi even though they can easily smell them. The second function actually increases the types of spore dispersers the fungi can interact with. Not all carrion feeders take to the sky. Many non-flying insects like centipedes and ants are limited to the forest floor. These organisms scurry around using their chemoreceptor packed antennae to find dead animals to feast on. The veil of Phallus indusiatus allows non-flying insects to crawl up and disperse the spore filled gleba.
What you will notice in every mature fruiting body of Phallus indusiatus is that the veil only just reaches the ground. It never levitates above the forest floor, and never has excessive folds that lay atop the soil and debris it saprophytically feasts on. This is a figment of stabilizing selection. Again, natural selection has favored the length of the veil to only reach the forest floor; nothing more, nothing less. Too short, and the crawling insects can’t utilize the veil as a ladder. Too long, and the fungus wastes resources it could have allocated to gleba production. This stabilizing selection should remind us of the Goldilocks’ concept involved with the, ‘just right’ length of the species veil.
I just love when people outside of the mycological realm take interest in the forest floor. We collectively must do our best to spread scientific knowledge. For too long science has been reserved for scientists. This is wrong, and has without a doubt, led us down a rather destructive path. People like you and me must stand against this archaic train of thought. Science is for the people! Don’t be intimidated! Embrace it! Learn about it! And for God’s sake, share the information you have with others! The more people that understand species interactions, the better chance we have at protecting Earth’s diverse ecosystems. Let this new year upon us be the year we revolt against scientific illiteracy!