Laetiporus sulphureus (Sulphur polypore)

Laetiporus sulphureus is a species of bracket fungus (fungi that grow on trees) found in Europe and North America. Its common names are crab-of-the-woods, sulphur polypore, sulphur shelf, and chicken-of-the-woods. Its fruit bodies grow as striking golden-yellow shelf-like structures on tree trunks and branches. Old fruitbodies fade to pale beige or pale grey. The undersurface of the fruit body is made up of tubelike pores rather than gills.

Laetiporus sulphureus is a saprophyte and occasionally a weak parasite, causing brown cubical rot in the heartwood of trees on which it grows. Unlike many bracket fungi, it is edible when young, although adverse reactions have been reported.

Taxonomy and phylogenetics
Laetiporus sulphureus was first described as Boletus sulphureus by French mycologist Pierre Bulliard in 1789. It has had many synonyms and was finally given its current name in 1920 by American mycologist William Murrill. Laetiporus means "with bright pores" and sulphureus means the colour of sulphur.

Investigations in North America have shown that there are several similar species within what has been considered L. sulphureus, and that the true L. sulphureus may be restricted to regions east of the Rocky Mountains. Phylogenetic analyses of ITS, nuclear large subunit and mitochondrial small subunit rDNA sequences from North American collections have delineated five distinct clades within the core Laetiporus clade:

• Conifericola clade: contains species that live on conifers, such as L. conifericola and L. huroniensis. All of the other tested species grow on angiosperms.
• Cincinnatus clade: contains L. cincinnatus
• Sulphureus clade I: contains white-pored L. sulfureus isolates.
• Sulphureus clade II: contains yellow-pored L. sulfureus isolates.
• Gilbertsonii clade: contains L. gilbertsonii and unidentified Caribbean isolates.

Description
The fruiting body emerges directly from the trunk of a tree and is initially knob-shaped, but soon expands to fan-shaped shelves, typically growing in overlapping tiers. It is sulphur-yellow to bright orange in color and has a suedelike texture. Old fruitbodies fade to tan or whitish. Each shelf may be anywhere from 5 to 60 centimetres (2 to 23 1⁄2 inches) across and up to 4 cm (1 1⁄2 in) thick. The fertile surface is sulphur-yellow with small pores or tubes and produces a white spore print. When fresh, the flesh is succulent with a strong fungal aroma and exudes a yellowish, transparent juice, but soon becomes dry and brittle.

Distribution and habitat
Laetiporus sulphureus is widely distributed across Europe and North America, although its range may be restricted to areas east of the Rockies. It grows on dead or mature hardwoods and has been reported from a very wide variety of host trees, such as Quercus, Prunus, Pyrus, Populus, Salix, Robinia, and Fagus, occasionally also from conifers, from August to October or later, sometimes as early as June. In the Mediterranean region, this species is usually found on Ceratonia and Eucalyptus. It can usually be found growing in clusters.
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