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Leucoagaricus
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Leucoagaricus

History

The genus Leucoagaricus was originally described as a subgenus of Leucocoprinus by Locquin in 1943. But in order to formalize a new genus in the scientific community, a description must contain a latin translation. Locquin did not provide this at the time, but Singer provided one in 1948 and moved Leucoagaricus to it's own independent genus. 

Leucoagaricus is a polyphyletic genus - meaning that it includes more than one genetic lineage. Due to limited genetic analysis to date, there will likely be many name changes in the future between Leucoagaricus, Leucocoprinus, and Lepiota. For now, many authors are using morphological characters, rather than genetic markers, as the primary instrument to characterize new species in the genus.

Leucoagaricus, Leucocoprinus, and Sericeomyces form one monophyletic clade in the Agaricaceae family. Leucoagaricus and Leucocoprinus form a monophyleltic clade, and should be thought of as one large group that needs taxonomic revision. Sericeomyces is a polyphyletic genus, meaning it will likely be split up in the future. These species contain a white, sericous (silk-like) cap surface.

Taxonomy

These are small to medium size mushrooms that can vary from small and fragile, to robust and fleshy. They generally grow from the ground - arising from dirt, leaf litter, well decomposed wood, or woodchips. The surface of the cap is also quite variable, from radially fibrillose (covered with silk-like fibers), to floccose (cottony), to squamulose (having small scales), to fibrillose-scaly. The margin of the cap is smooth to short-striate. Gills are free from the stem. The stem is central to the cap, and is usually equal, although it can sometimes develop a bulb at the base. There is usually a membranous and persistent ring on the stem.

The genus Leucoagaricus is characterized by:

  • a smooth (entire) or rarely lined margin to the cap
  • free gills
  • spores that give a red reaction in cresyl blue (metachromic)
  • absence of clamp-connections
  • abesense of pseudoparaphyses around the basidia (absense of modified terminal hyphae in the hymenium [sprore bearing layer])
The genus Leucocoprinus has a lined margin to the cap and has pseudoparaphyses around the trimorphic basidia. 

Leucoagaricus sect. Annulati
Characterized by:
  • Fleshy cap
  • White gills that can stain yellow
  • Cap surface that breaks into fibrillose-squamulose scales 
  • Almond shaped pores with evident germ pore
Species:
Leucoagaricus americanus (Type)
Leucoagaricus leucothites

Two subsections:
  • Rubescentes - 
  • Unknown - 
Leucoagaricus sect. Rubrotincti
Characterized by:
  • Pigmented cap
  • Smooth basidiospores with inconspicuous or absent germ pore
  • Flesh does not bruise when handled
  • Flesh does not stain blue-green with NH4 (ammonia)
Leucoagaricus sect. Piloselli
Characterized by:
  • Flesh stains red when handled
  • Flesh stains blue-green with NH4 (ammonia)
Two subsections:
  • Pilatianei - absense of an apical outgrowth on cheilcystidia
  • Pilosellini - presence of an apical outgrowth on cheilcystidia
Species of sect. Piloselli:
Lepiota besseyi
Lepiota castanescens
Lepiota decorata
Lepiota flammeotincta
Lepiota fuliginescens 
Lepiota mutata - white scaly species from Kansas that turns brown upon drying. 
Lepiota muticolor - described from Alabama.
Lepiota roseifolia
Lepiota roseolivida
Lepiota sanguiflua - from Florida.
Lepiota tinctoria - from Florida.
Leucoagaricus adelphicus
Leucoagaricus americanus
Leucoagaricus brunnescens 
Leucoagaricus cupresseus
Leucoagaricus dyscritus
Leucoagaricus erythrophaeus
Leucoagaricus flammeotincoides 
Leucoagaricus hesperius
Leucoagaricus marginatus 
Leucoagaricus meleagris 
Leucoagaricus pardalotus 
Leucoagaricus pyrrhophaeus
Leucoagaricus pyrrhulus 

 

References:

Liang et al. (2010). Two new unusual Leugoagaricus species from tropical China with blue-green staining reactions. Mycologia 102 (5) : 1141 - 1152. Link
Ortiz et al (2008). A new species of Leucoagaricus (Agaricaceae) from Columbia. Mycotaxon. 106: 371-378. Link
Vellinga (2010). Lepiotaceous fungi in California, USA. Leucoagaricus sect. Piloselli. Link
Vellina & Davis (2006).  Lepiotaceous fungi in California USA. Leucoagaricus amanitoides sp. nov. Mycotaxon 98: 197 - 204. Link

Page Created: 12/7/13
Last Updated: 12/7/13