Introduction to Mycology

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Introduction to Mycology

• General Mycology Lecture 1
• Pl P 421/521

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What is a fungus?

• A eukaryotic, heterotrophic organism devoid of
  chlorophyll that obtains its nutrients by
  absorption, and reproduces by spores.
• The primary carbohydrate storage product of fungi
  is glycogen.
• Most fungi have a thallus composed of hyphae
  (sing. hypha) that elongate by tip growth

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Fungal hyphae form a network called a mycelium
(pl. mycelia)
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• Carl Linnaeus (1707-1778) the Father of
  Taxonomy
• Minerals exist plants exist and live animals
  exist, live and sense.
• Plants without obvious sexual organs were
  classified in Class Cryptogamia (lichens, fungi,
  mosses, ferns)
• Fungi are primitive plants under this
  classification of organisms.

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R. H. Whittakers 1969 Classification
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Modern Classification

• At least 7 kingdoms are now recognized
• Eubacteria, Archaebacteria, Animalia, Plantae,
  Eumycota, Stramenopila (Chromista), Protoctista
  (Protozoa, Protista)

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Fungi versus fungi

• fungus is used inclusively for a heterogenous
  group of organisms that have traditionally been
  studied by mycologists
• Fungi refers to the organisms in the Kingdom
  Fungi, the true fungi, also called the Eumycota

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• Kingdom Fungi
• Phyla Chytridiomycota
• Zygomycota
• Glomeromycota
• Ascomycota (inc.Deuteromycetes)
• Basidiomycota

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• Kingdom Stramenopila (Chromista)
• Phyla Oomycota
• Hyphochytriomycota
• Labyrinthulomycota
• Protists (Protoctists)
• Phyla Plasmodiophoromycota
• Dictyosteliomycota
• Acrasiomycota
• Myxomycota

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• Hierarchical Classification
• Kingdom Fungi
• Phylum Basidiomycota
• Class Basidiomycetes
• Order Agaricales
• Family Agaricaceae
• Genus Agaricus
• Species
• Agaricus campestris L.

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Agaricus campestris L.

• Agaricus is the genus
• campestris is the specific epithet
• The genus species is the Latin binomial note
  that the genus and species are in italics (or
  underlined), the genus is capitalized and the
  species epithet is in lower case
• L. stands for Linnaeus, the authority
• Agaricus campestris is the type species of the
  genus

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Agaricus bisporus (Lange) Imbach

• Lange first described this fungus as Coprinus
  bisporus
• Imbach later transferred the species to Agaricus

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Nomenclature

• Nomenclature the allocation of scientific
  names to the units a systematist considers to
  merit formal recognition. (Hawksworth et al.,
  1995. The Dictionary of the Fungi). 
• The nomenclature of fungi is governed by the
  International Code for Botanical Nomenclature, as
  adopted by the International Botanical Congress.

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Typological Species Concept

• "Species are as many as were created in the
  beginning by the Infinite."   (Linnaeus, 1758)
• Each species represented by a type specimen,
  designated in the original description and
  deposited in a recognized collection (eg.,
  herbarium)
• The name is tied to the type specimen
• The type specimen is not necessarily typical of
  the entire species!

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How are fungi named?

• To determine the correct name for a taxon,
  certain steps must be followed, including
• Effective publication
• Valid publication
• Description or diagnosis in Latin
• Clear indication of rank
• Designated type

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How many species of fungi exist?

• 80,000 species of fungi described
• 1,700 new species described each year

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Estimating the number of fungal species

• Hawksworth, D. L. (1991). The fungal dimension
  of biodiversity magnitude, significance, and
  conservation. Mycological Research 95 641-655
• Hawksworth, D.L. (2001) The magnitude of fungal
  diversity the 1.5 million species estimate
  revisited. Mycological Research 105 (12)
  1422-1432.

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Fungi are ancient

• Major fungal lineages are ancient, perhaps
  emerging one billion years ago
• Fungi were present before the emergence of
  animals and vascular plants

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Mass extinction at K-T boundary fungal spike
Increasing diversity of angiosperms, mammals,
birds
Gymnosperms dominant, evolution of angiosperms
first birds
Gymnosperms become dominant, first dinosaurs,
first mammals
Mass extinction of 95 of all species
fungal spike
Origin of insects, ferns, seed plants
Earliest terrestrial vascular plants
marine animals diversify first appearance of
most animal phyla diverse algae
Modified from Blackwell, 2001
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Associations

• Fungi form symbiotic relationships with a number
  of organisms
• Lichens
• Mycorrhizas
• Endophytes

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Decomposers

• As saprotrophs, particularly as decomposers,
  fungi are essential components of the carbon
  cycle and are among the few organisms that can
  break down lignin

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Pathogens

• Fungi are important as pathogens of animals and
  plants.
• Over 70 of all plant diseases are caused by
  fungi

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