Polypore

Source: Wikipedia, the free encyclopedia.
(Redirected from
Bracket fungi
)
"Conks" redirects here. For the British submarine, see HMS Conqueror (S48). For the hairstyle, see Conk.
Polypores (Ganoderma sp.) growing on a tree in Borneo

Polypores are a group of

fruiting bodies that are called conks.[1]

Most polypores inhabit tree trunks or branches consuming the wood, but some soil-inhabiting species form mycorrhiza with trees. Polypores and the related corticioid fungi are the most important agents of wood decay, playing a very significant role in nutrient cycling and aiding carbon dioxide absorption by forest ecosystems.[2]

Over one thousand polypore species have been described to science,[3] but a large part of the diversity is still unknown even in relatively well-studied temperate areas. Polypores are much more diverse in old natural forests with abundant dead wood than in younger managed forests or plantations. Consequently, a number of species have declined drastically and are under threat of extinction due to logging and deforestation.

Polypores are used in traditional medicine, and they are actively studied for their medicinal value and various industrial applications. Several polypore species are serious pathogens of plantation trees and are major causes of timber spoilage.

Trametes versicolor, a colorful bracket fungus, commonly known as turkey tail[4]
A bracket fungus (Pycnoporus sp.) with a tough, woody cap
blushing bracket showing the red bruising, which is one identification characteristic[4]
Laetiporus sulphureus
Bracket fungus on tree in Tokyo, Japan

Conks, the fruiting bodies of polypores, lie in a close planar grouping of separate or interconnected horizontal rows. Brackets can range from only a single row of a few caps, to dozens of rows of caps that can weigh several hundred pounds. They are mainly found on trees (living and dead) and coarse woody debris, and may resemble mushrooms. Some form annual fruiting bodies while others are perennial and grow larger year after year. Bracket fungi are typically tough and sturdy and produce their spores, called basidiospores, within the pores that typically make up the undersurface.

Classification

Because bracket fungi are defined by their growth form rather than

dryad's saddle, artist's conk, and turkey tail. The name polypores is often used for a group that includes many of the hard or leathery fungi, which often lack a stipe, growing straight out of wood. "Polypore" is derived from the Greek words poly, meaning "much" or "many", and poros, meaning "pore".[5]

The group includes many different shapes and forms that are common in the tropical forests, including the hard 'cup fungi' and the 'shell', 'plate' and 'bracket' fungus commonly found growing off logs and still standing dead trees.

Description

Schematic drawing of a pileate polypore fruit body

The fungal individual that develops the fruit bodies that are identified as polypores resides in soil or wood as

Piptoporus betulinus on birch, Perenniporia corticola on dipterocarps
).

Forms of polypore fruit bodies range from mushroom-shaped to thin effused patches (crusts) that develop on dead wood. Perennial fruit bodies of some species growing on living trees can grow over 80 years old (e.g. Phellinus igniarius).[6] Most species of polypores develop new, short-lived fruit bodies annually or several times every year. Abundant fruit takes place during the autumn or rainy season.

Structure of the fruit bodies is simple. Effused or resupinate fruit bodies typically consist of two layers - a tube layer of vertically arranged tubes that open downwards, and supporting layer called subiculum that supports and attached the tubes to substrate. In fruit bodies with a cap (pileate fruit bodies) the tissue between upper surface and the pore layer is called context. A few polypores (e.g. Fomes fomentarius and Inocutis rhaedes) also have a core between context and substrate. A minority of polypores also have a stalk (stipe) that attach to the cap either laterally or centrally depending on the species.

Polypore tubes are a honeycomb-like structure, where the individual tubes have fused together. Their sides are covered with a spore-forming surface, the

conidia) in the upper surface of their cap (e.g. Echinopora aculeifera, Oligoporus ptychogaster) or without the presence of a sexual fruit body (e.g. Inonotus rickii, Heterobasidion spp.).[7]

  • Polyporus sp. fruit bodies with stalk (Indonesia)
    Polyporus sp. fruit bodies with stalk (Indonesia)
  • Perennial conk of Fomitopsis pinicola on spruce
    Perennial conk of Fomitopsis pinicola on spruce
  • Effused fruit bodies of Meruliopsis taxicola on a pine log
    Effused fruit bodies of Meruliopsis taxicola on a pine log
  • bottom side polypore with pores/tubes clearly visible
    bottom side polypore with pores/tubes clearly visible

Ecology

Bracket fungi often grow in semi-circular shapes, looking like trees or wood. They can be

genera, Ganoderma
, can grow large thick shelves that may contribute to the death of the tree, and then feed off the wood for years after. Their hardiness means they are very resilient and can live for quite a long time, with many species even developing beautiful multi-coloured circles of colour that are actually annual growth rings. Polypores are among the most efficient decomposers of lignin and cellulose, the main components of wood. Due to this ability they dominate communities of wood-rotting organisms in land ecosystems along with corticioid fungi. Through decomposing tree trunks they recycle a major part of nutrients in forests.[8]

Only basidiomycetes are known to initiate lignin degradation (i.e. cause white rot). A 2012 study linked the end of formation of large-scale coal deposits in the end of the Carboniferous period 300 million years ago to the evolution of lignin-degrading basidiomycetes.[9] More efficient degradation of wood by fungi meant less plant material (and hence less coal) accumulating in the soil.

On the other hand, most brown-rot fungi are polypores. These species have lost their lignin degradation ability but are very efficient in degrading cellulose. Brown-rot fungi are prevalent on conifer hosts and open, sun-exposed habitats. The fungal community in any single trunk may include both white-rot and brown-rot species, complementing each other's wood degradation strategies.

Polypores and other decomposer fungi are the first step in food chains that feed on decomposed plant material. A rich fauna of insects, mites and other invertebrates feed on polypore mycelium and fruiting bodies, further providing food for birds and other larger animals. Woodpeckers and other hole nesting birds typically carve their nests in softer wood decomposed by polypores.[10]

Threats

Almost all polypores are dependent on trees for their survival. Deforestation and intensive forest management cause declines in polypore abundance and diversity. For many species the changes can be too much, and they start a slow slide towards extinction. Since most polypore species are relatively widespread, this process is typically slow. Regional extinctions can happen relatively quickly and have been documented (for instance Antrodia crassa in North Europe[11]).

Polypores can decline for many reasons. They can be dependent on a single host or a very special habitat. For instance

Bridgeoporus nobilissimus of the Northwestern USA.[14]
Both of these species also have a rather restricted range, making them more vulnerable to extinction.

In addition to the host tree individual, the characteristics of the surrounding habitat also matter. Some species prefer closed-canopy forest with a moist, even microclimate that could be disturbed for instance by logging (e.g.

Skeletocutis jelicii). Others suffer from lack of open forest-fire habitat in areas where fire suppression is done (e.g. Gloeophyllum carbonarium in Nordic countries where forest fires are part of the natural forest dynamics).[15]

For most declining species the main problem is lack of dead wood in the forest. When suitable tree trunks are too sparse in the landscape, not all species are able to spread to new trunks after old ones have been consumed, causing the population to decline and eventually vanish. Thus, species that are abundant in

Fomitopsis rosea
are dominant species in North European old-growth spruce forests from Poland to Norway, but absent in managed forests.

Climate change may cause a problem for polypores that are already dependent on a few fragments of old-growth forests and may be unable to migrate with changing vegetation.

Indicator value

Polypores have been used as indicator species of healthy natural forests or

old-growth forests in Europe. They are good indicators of invertebrate diversity on dead wood and include many endangered species. Polypores make good indicators because they are relatively easy to find – many species produce conspicuous and long-lasting fruiting bodies – and because they can be identified in the field.[16]

The first indicator list of polypores widely used in forest inventories and conservation work was developed in northern Sweden in 1992 ("Steget före" method).[17][18] "Steget före" list included six polypores in three value classes. In Finland, a list of 30 species for spruce-dominated forests was published in 1993 and widely adopted.[19] Later a similar list for pine-dominated forests was published. Longer lists of indicator species have since been published in Sweden.[20][21]

Many indicator species are

red-listed
, but not necessarily all. National red lists of fungi typically include many polypores and are used as indicator lists of conservation value in many European countries.

Classification

For most of 20th century polypores were treated as a family, the Polyporaceae. Reconstructions of family trees of fungi show that the

Trechisporales
.

The Polyporales in the modern sense are not only polypores but also other fruiting body types such as crust fungi, hydnoid fungi and agaricoid mushrooms. The term polypore describing a morphological group should not be confused with the taxonomic groups Polyporales or Polyporaceae of the modern literature.

Currently polypores are divided into about 170 genera.[26][27] That number is bound to rise significantly through better understanding of evolutionary relationships between species and through mapping of uncovered diversity in the tropics. All in all classification of polypores is in flux.[28]

Delimitation (morphology)

Most polypores have a poroid hymenium, but not all species. A few, for instance Elmerina holophaea and

Lenzites betulina, form gills like agarics but are still considered polypores, since in all other respects they are similar to closely related polypores, forming tough fruiting bodies on the wood. A couple of species where the tubes have not fused together in a honey-comb manner are variably classified as polypores or not (e.g. Porotheleum fimbriatum). There's no clear distinction between polypores and hydnoid fungi - some polypores with irregularly poroid lower surface have been considered both polypores and hydnoid fungi (e.g. Echinodontium tinctorium, Irpex lacteus
).

Bolete mushrooms are a separate morphological group not included in polypores even though they have tubes. Fleshy fruiting bodies with a stalk and microscopic characters separate boletes from polypores.

  • Irpex lacteus with irregular pores
    Irpex lacteus with irregular pores
  • Elmerina holophaea, a polypore with gills
    Elmerina holophaea, a polypore with gills

Uses

Some species of bracket fungi are edible, such as

lingzhi mushroom
is another, which is used in Chinese medicine. They can also be used as a wick in an oil/fat lamp.

The tinder fungus (Fomes fomentarius) has been used as tinder since at least the time of Ötzi the Iceman. It has also been used to make a material similar to leather.

Ganoderma applanatum, the artist's conk, is used as a substrate for drawings. Fresh specimens develop dark brown lines when drawn upon with a stylus. The lines become permanent when the specimen is dried.[30]

Medicinal uses

Main article:
Medicinal fungi

Most polypores are edible or at least non-toxic, however one genus of polypores has members that are

Piptoporus betulinus, notable for its long usage in European folk medicines,[32] and Fomes fomentarius, which was likely used for starting fires.[33]

herbal medicine, contemporary research has suggested many applications of polypores for the treatment of illnesses related to the immune system and cancer
recovery.

Several species have been studied for their ability to produce compounds with anti-pathogenic activity.[35][36]

See also

References

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External links
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