About the Amanitaceae

The family Amanitaceae R. Heim ex Pouzar (the Amanita family) is typified by the genus Amanita Pers. and presently comprises two genera: Amanita and Limacella Earle.  In most of the world, the species in these two genera are gilled mushrooms with central stipes.  It is very likely that the genus Amanita will be found to contain 1,000 or more taxa (over 868 are listed on this site, with undetected taxa highly likely).  So far as is known, the genus Limacella is much smaller—apparently an evolutionary relict group—with, perhaps, 60 - 100 species to be expected (57 are now listed on this site, with some synonymy among those names expected).

The small number of taxa not having an agaricoid habit (that is not taking the form of a gilled mushroom with a central stem) occur in arid, often sandy areas where rain is seasonal and not well retained in the ecosystem——(a) countries surrounding the Mediterranean (one species) and (b) southwestern Australia (about a half-dozen species).  These exceptions were initially treated in two genera—Amarrendia Bougher & T. Lebel and Torrendia Bres.—that are now considered synonyms of Amanita.

Recent (including some unpublished) molecular studies concur with the morphological view that Limacella is a distinct and older (more basal) genus than Amanita, and that the two share a common ancestor.

Agaricoid forms

All agaricoid taxa in the Amanitaceae have two, defining, microscopic characters in common:
  • a cross-section of a gill will reveal that the gill’s tissue (lamella trama) has an interior structure that is some variation of a constant theme—if you imagine a line running down the center of the cross-section from the connection of the gill to the cap to the gill’s free edge, (1) the two halves of the gill divided by that line are approximate mirror images of each other and (2) the tissues on both sides of the center line are composed of cells that individually and in groups are clearly curving away from the center line.  This anatomical structure is called a bilateral, divergent lamella trama.

  • a thin, vertical slice of the stem tissue will always reveal vertically aligned inflated cells that are shaped like clubs or baseball bats, these may be in short chains in some taxa, but are more commonly solitary and arising from the end of a simple hypha.  This sort of inflated cell has been given a technical name “acrophysalide.”  Stem tissue with such a structure is called longitudinally acrophysalidic.  It is unknown outside of the family Amanitaceae . It is persistent—even after an amanita has been chopped and thoroughly cooked and been in a poisoning victims stomach, the fact that the tissue is longitudinally acrophysalidic can be determined with a microscope.
Sequestrate forms

What about the taxa formerly placed in the genera Amarrendia and Torrendia?

Both of these genera included sequestrate species—species that had lost the ability to auto-eject spores from their basidia—they "sequester" their spores.  These species retain basidia; and some of the cellular structure of gills is also preserved; but true gills no longer exist.  The term that is used for the tissue in which spores develop in common puffballs and truffle-like basidiomycetes—“gleba”—is used for the spore bearing tissue in the truffle-like amanitas formerly placed in Amarrendia.  The term “lamella trama” is not applicable.

On the other hand, the former members of the genus Torrendia all have a stem.  The stem was little affected by the evolutionary changes that produced the secotioid (“puffball on a stick”) form of the species of Torrendia.  One of the consequences is that the stem of an Amanita formerly placed in Torrendia is longitudinally acrophysalidic.

The taxa formerly placed in Torrendia comprise the epigeous (above ground) sequestrate forms in Amanita, and the taxa formerly placed in Amarrendia comprise the hypogeous (underground), truffle-like species of Amanita.  A number of hypogeous amanitas have retained an internal element called a columella, which is the remnant of a stem much altered by evolution, but still including the typical longitudinally acrophysalidic tissue.

The hypogeous forms that have been most altered by evolution have been confirmed to belong in Amanita only by genetic sequencing. Hence, membership of sequestrate forms in the Amanitaceae may be supported by study of microscopic anatomy in a number of cases.  However, the current status of the family relies on concise definitions of the family and its two genera based on the agaricoid taxa with supplemental reliance on genetic similarity to support inclusion of the sequestrate taxa.
For more about taxonomic impact of the inclusion of Amarrendia and Torrendia in Amanita, see the draft essay concerning Amanita sect. Caesareae (here).  Please note that this document is in draft and is known to contain taxonomic and systematic problems still under discussion.

To continue with a taxonomic summary of the Amanitaceae, please explore the "About..." links at left.
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