Figure 23. Puccinia monoica is a complex that uses volatiles to induce its host to create “pseudoflowers.”26 Photo Anne Elliott.


truffle; Fig. 21) and Tuber magnatum (the white truffle). Since truffles develop below ground, they are completely dependent on other organisms for spore dispersal. Ripened truffles release a mixture of pungent sulfur-based volatiles that diffuse up through the substratum and into the open air. Mammalian and invertebrate foragers attracted by the odors unearth and eat the truffles, and later spread the spores via their feces.25 Stinkhorns are olfactory paradoxes. Growing above ground, their rancid sulfur-based volatiles are offensive to some creatures but readily attract flies, beetles and other insects who feed on their spore-filled slimy caps (Fig. 22). Te spores are then dispersed into new habitats when they pass unharmed through the insects’ digestive tracts.20 Some fungi use volatiles to induce their hosts to form “pseudoflowers” that visually and olfactorily mimic nectar rewards and floral fragrances to attract spore vectors (Fig. 23).


Are mushroom


odors aposematic? Tat predators use odors to avoid


unpalatable prey was first hypothesized decades ago,27


but it was not until 1981 Fall 2021 FUNGI Volume 14:4 51


Figure 24. Amanita bisporigera, the destroying angel, can be mistaken for a couple of common edibles. It can be lethally toxic with an odor not distinctive in young specimens, but often becoming sickly sweet or reminiscent of rotting meat with age. Is this a warning to vertebrate mycophages and paradoxically an attractant to invertebrate mycophages? Photo Renée Lebeuf.


that two researchers coined the term “olfactory aposematism” to explain their theory.28


suggests that organisms secondarily defended by toxins, poisons, or bitter tastes, will also signal their unprofitability via an odor.29


Olfactory aposematism Odors, as


warning signals, have several advantages over color, the trait on which aposematic theory was founded. Odors can be more effective at warning nocturnal


predators whose night vision is usually blind to color. Odors can also signal unprofitability over longer distances and often circumvent line-of-sight barriers that could lead to inadvertent predator-prey contact.30,31


Do these


advantages also apply to mushroom odors and do poisonous mushrooms use odors to signal their unprofitability? As with color, there is simply not enough research to give definitive answers yet.


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