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Controversy over Hygrophorus cossus settled using ITS sequence data from 200 year-old type material
Ellen Larsson1, Stig Jacobsson
1Botanical Institute, Göteborg University, SE-405 30 Göteborg, Sweden. ellen.larsson@botany.gu.se
Mycological Research
|September 28, 2004
Summary
The fungus Agaricus cossus, now in Hygrophorus, has a distinctive smell. DNA sequencing confirms it is an older name for Hygrophorus quercetorum, a species associated with oak trees.
Area of Science:
- Mycology
- Fungal Taxonomy
- Molecular Phylogenetics
Background:
- Agaricus cossus was described in 1799, noted for its unique smell reminiscent of Cossus cossus larvae.
- This species belongs to the Hygrophorus genus, but its specific epithet has been inconsistently applied due to multiple white Hygrophorus species sharing this aroma.
Observation:
- The internal transcribed spacer (ITS) region from the original 1794 type collection of H. cossus was successfully sequenced.
- Morphological and ecological characteristics, including basidiome color changes with age and host tree association, were examined.
Findings:
- DNA sequencing and comparison with related species, including the type specimen of H. quercetorum, revealed that H. cossus is an older name for H. quercetorum.
- H. cossus is specifically associated with Quercus (oak) trees.
Implications:
- Clarifies the taxonomic identity of H. cossus, resolving long-standing ambiguity.
- Provides key morphological and ecological discriminators for differentiating closely related Hygrophorus species with similar aromatic properties.
- Enhances understanding of fungal diversity and host associations within the Hygrophorus genus.