''Fomitopsis betulina'' (previously ''Piptoporus betulinus''), commonly known as the birch polypore, birch bracket, or razor strop, is a common
bracket fungus and, as the name suggests, grows almost exclusively on
birch trees. The brackets burst out from the bark of the tree, and these
fruit bodies can last for more than a year.
Taxonomy
The fungus was originally
described by
Jean Bulliard in 1788 as ''Boletus betulinus''.
It was transferred to the genus ''
Piptoporus'' by
Petter Karsten
Petter Adolf Karsten (16 February 1834 – 22 March 1917) was a Finnish mycologist, the foremost expert on the fungi of Finland in his day, and known in consequence as the "father of Finnish mycology".
Karsten was born in Merimasku near Turku ...
in 1881.
Molecular phylogenetic
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
studies suggested that the species was more closely related to ''
Fomitopsis'' than to ''Piptoporus'',
and the fungus was reclassified to ''Fomitopsis'' in 2016.
The
specific epithet
In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''betulina'' refers to the genus of the
host plant (''
Betula'').
Common name
In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...
s for the fungus include birch bracket,
birch polypore, and razorstrop fungus.
Description
The fruit bodies (
basidiocarps) are pale, with a smooth greyish-brown top surface, while the creamy white underside has hundreds of pores that contain the
spore
In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
s. The fruit body has a rubbery texture, becoming corky with age.
Wood decayed by the fungus, and cultures of its
mycelium
Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...
, often smell distinctly of green apples.
The
spore
In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
s are cylindrical to
ellipsoidal in shape, and measure 3–6 by 1.5–2
μm.
''Fomitopsis betulina'' has a
bipolar mating system where
monokaryons or germinating spores can only mate and form a fertile
dikaryon with an individual that possesses a different mating-type factor. There are at least 33 different mating-type factors within the British population of this fungus.
These factors are all variants or
allele
An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule.
Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...
s of a single gene, as opposed to the
tetrapolar mating system of some other
basidiomycete species, which involves two genes.
Distribution, habitat and ecology
''Fomitopsis betulina'' is one of the most common species of
brown rot fungi.
The geographic distribution of ''F. betulina'' appears to be restricted to the
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...
, including Northern America, Europe, and Asia.
It is only found on
birch trees, including ''
Betula pendula'', ''
B. pubescens'', ''
B. papyrifera'', and ''
B. obscura''.
There is some doubt about the ability of isolates from the European continent, North America and the British Isles to interbreed.
It is a necrotrophic
parasite
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
on weakened birches, and will cause brown rot and eventually death, being one of the most common fungi visible on dead birches. It is likely that the birch bracket fungus becomes established in small wounds and broken branches and may lie dormant for years, compartmentalised into a small area by the tree's own defence mechanisms, until something occurs to weaken the tree. Fire, drought and suppression by other trees are common causes of such stress.
In most infections there is only one fungal individual present, but occasionally several individuals may be isolated from a single tree, and in these cases it is possible that the birch bracket fungus entered after something else killed the tree. These fungal "individuals" can sometimes be seen if a slice of brown-rotted birch wood is incubated in a plastic bag for several days. This allows the white
mycelium
Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...
of the fungus to grow out of the surface of the wood. If more than one individual
dikaryon is present, lines of
intraspecific antagonism form as the two individual mycelia interact and repel each other.
The fungus can harbor a large number of species of insects that depend on it for food and as breeding sites. In a large-scale study of over 2600 fruit bodies collected in eastern Canada, 257 species of arthropods, including 172 insects and 59 mites, were found.
The fungus is eaten by the
caterpillars of the
fungus moth ''
Nemaxera betulinella''.
Old fruit bodies that have survived the winter are often colonized by the white to pale yellow fungus ''
Hypocrea pulmonata''.
Research on chemical constituents
''Fomitopsis betulina'' has been widely used in
traditional medicine
Traditional medicine (also known as indigenous medicine or folk medicine) refers to the knowledge, skills, and practices rooted in the cultural beliefs of various societies, especially Indigenous groups, used for maintaining health and treatin ...
s, and has been extensively researched for its
phytochemistry and
pharmacological activity.
Phytochemicals include
phenolic acids,
indole compounds,
sterol
A sterol is any organic compound with a Skeletal formula, skeleton closely related to Cholestanol, cholestan-3-ol. The simplest sterol is gonan-3-ol, which has a formula of , and is derived from that of gonane by replacement of a hydrogen atom on ...
s, and
triterpenes, especially
betulin and
betulinic acid.
Agaric acid, found in the fruit body of the fungus, is poisonous to the parasitic
whipworm ''Trichuris trichiura''.
The fungus was carried by "
Ötzi the Iceman" – the 5,300 year old
mummy
A mummy is a dead human or an animal whose soft tissues and Organ (biology), organs have been preserved by either intentional or accidental exposure to Chemical substance, chemicals, extreme cold, very low humidity, or lack of air, so that the ...
found in
Tyrol, with speculation that the fungus may have been used as a
laxative to expel whipworm.
Uses
The velvety cut surface of the fruit body was traditionally used as a
strop for finishing the edges on razors,
and as a mounting material for insect collections.
It has also been used as
tinder and
anesthetic.
[
It is considered inedible.]
See also
*''Fomes fomentarius
''Fomes fomentarius'' (commonly known as the tinder fungus, false tinder fungus, hoof fungus, tinder conk, tinder polypore or ice man fungus) is a species of fungi, fungal plant pathogen found in Europe, Asia, Africa and North America. The spec ...
'', another fungus carried by Ötzi the Iceman
References
*
{{Taxonbar, from1=Q96894257, from2=Q865591
Fomitopsidaceae
Fungi described in 1788
Medicinal fungi
Fungi of Asia
Fungi of Europe
Fungi of North America
Inedible fungi
Parasitic fungi
Taxa named by Jean Baptiste François Pierre Bulliard
Fungus species
Ötzi