#046: Mushroom Morphology: False Truffles

False truffles are basidiomycetes that produce fruiting bodies at or below the soil surface (hypogeous). These mushrooms are included in the gasteromycetes because they develop their spores internally and have lost the ability to forcibly discharge their spores.  Like the true truffles, false truffles disperse their spores by attracting animals like insects, rodents, and deer.  False truffles secrete scents to attract these animals, which eat the mushrooms and spread the spores around in their feces.  Most false truffles have a gleba (the internal, spore-producing tissue) that is divided up into small chambers called locules.  Many false truffles also have a short stipe at the base or a stipe-columella that extends into the gleba as a branching structure.  Aside from the stipe-columella, the gleba of false truffles is fairly regular in appearance.  This easily separates them from true truffles, which appear marbled when sliced in half.

False truffles evolved from more familiar mushrooms like agarics and boletes by following the same evolutionary pattern as the sequestrate fungi (see FFF#045).  These fungi originally adapted to successfully spread their spores in arid climates, but are now widely distributed.  In order to retain moisture during spore development, the ancestors of false truffles stopped opening their caps at maturity.  Eventually ballistospory was lost.  Because these fungi relied on animals to disperse their spores, they no longer needed a stipe.  As a result, the stipe gradually became shorter and these mushrooms ceased to be lifted above the ground.  Once the reproductive tissue was completely enclosed, the original gills or pores became compact and fused, resulting in the locules found in false truffles today.

As with the sequestrate fungi, the false truffles are an unnatural group (polyphyletic).  Although they share a common morphology, ecology, and life history strategy, they are often not closely related to one another.  Once again, the fungi have given us an excellent example of convergent evolution.  False truffles have evolved from agarics, russulas, boletes, and chanterelles, among others.  Despite these diverse origins, all false truffles are mycorrhizal with trees and shrubs.  Many false truffles show a high degree of host specificity.  Some of these fungi will only associate with either hardwoods or conifers while others will only associate with a handful of (or even a single) plant species.   None of the false truffles are considered edible, although most are nonpoisonous.

See Further:

http://website.nbm-mnb.ca/mycologywebpages/NaturalHistoryOfFungi/FalseTruffles.html

http://www.mykoweb.com/systematics/literature/The%20Secotioid%20Syndrome.pdf (an academic paper)

Miller and Miller, “North American Mushrooms…”: http://books.google.com/books?id=zjvXkLpqsEgC&pg=PA483&lpg=PA483&dq=false+truffles&source=bl&ots=J3i3A_e0Bi&sig=aY_livzfFUwH5crx5GtICNnLaoU&hl=en&sa=X&ei=qTLIU8raEMzlsATYv4CoDg&ved=0CD8Q6AEwAzgK#v=onepage&q=false%20truffles&f=false