Agaricales

The order Agaricales, also known as gilled mushrooms (for their distinctive gills), or euagarics, contains some of the most familiar types of mushrooms. The order has about 4,000 identified species, or one quarter of all known homobasidiomycetes. They range from the ubiquitous common mushroom to the deadly destroying angel and the hallucinogenic fly agaric to the bioluminescent jack-o-lantern mushroom.

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Classification

Some notable fungi with gill-like structures, such as chanterelles, have long been recognized as being substantially different from usual Agaricales. Interestingly, molecular studies are showing more groups of agarics as being more divergent than previously thought, such as the genera Russula and Lactarius belonging to a separate order Russulales, and other gilled fungi, including such species as Paxillus involutus and Hygrophoropsis aurantiaca showing a closer affinity with Boletes in the order Boletales.

Also, some other quite distinctive fungi, the puffballs and the Beefsteak fungus have been recently been shown to lie within the Agaricales.

The term agaric had traditionally referred to Agaricales, which were defined as exactly those fungi with gills. Given the discoveries described above, those two categories are not synonymous (although there is a very large overlap between the two groups).

Distribution and habitat

Agarics are ubiquitous, being found across all continents. Most are terrestrial, their habitats including all types of woodland and grassland, varying largely from one genus to another.

Characteristics

Basidiocarps of the agarics are typically fleshy, with a stipe, often called a stem or stalk, a pileus (or cap) and lamellae (or gills), where basidiospores are produced. This is indeed the stereotyped structure of what we would call a mushroom.

Life cycle

The agarics' life cycle is very much representative of the basidiomycetes. Clamp connections are present in the dikaryons of many species. The agarics always have their basidiospores ejected from the basidium into the area between gill edges. The spores are then let fall to the ground or carried by the wind.

References

• The Gilled Mushrooms ("Agaricales")

• Moncalvo JM, et al. 2002. One hundred and seventeen clades of euagarics. Molecular Phylogenetics and Evolution 23:357-400. Available from: http://www.botany.utoronto.ca/faculty/moncalvo/117clade.pdf

• Tree of Life: Agaricales