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Recent (including some unpublished) molecular studies concur with the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.
