Systematics of the Glomeromycota

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Systematics of the Glomeromycota

• FROM ENDOGONE TO THE GLOMEROMYCOTA IN 200
  YEARS

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These slides summarise an introduction given at
the COST 8.38 meeting in Granada on 21st October
by Peter Jeffries and are intended to give a
brief overview of the history of the systematics
of the Glomeromycota. The Glomeromycota is the
taxon that comprises the arbuscular mycorrhizal
fungi. It had its beginnings almost two hundred
years ago when the first spores of AMF were
described as members of the genus Endogone.
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Past History

• 1809 Endogone established as a genus probably
  within the Ascomycota by Link
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• 1845 Glomus introduced by Tulasne Tulasne
• Synonymised with Endogone in 1851  
• 1922 Endogonaceae proposed as a family of
  Mucorales by Thaxter
•  
• 1953 Endogonales proposed by Moreau but not
  formally adopted

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Past History 2

• 1974 The genera Acaulospora, Endogone, Glaziella,
  Glomus, Gigaspora, Modicella, Sclerocystis
  established by Gerdemann Trappe
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• 1979 Endogonales accepted by Benjamin
• Entrophospora described by Ames Schneider
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• 1986 Scutellospora described by Walker Sanders

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Recent Developments

• 1990 Glomales proposed by Morton Benny
  comprising of two groups and three families
• Glominae
• Glomaceae (Glomus, Sclerocystis)
• Acaulosporaceae (Acaulospora, Entrophospora)
• Gigasporineae
• Gigasporaceae (Gigaspora, Scutellospora)

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Molecular Analyses
In the last decade, new molecular analyses have
shown that systematics based solelly on
morphological criteria are often flawed. As a
result, new schemes have been proposed in which
molecular characters have deteremined the major
clades. The AMF are no exception and in 2001
Morton Redecker erected two new families and
genera based on molecular criteria Archaeospora
ceae (Archaeospora) Paraglomaceae (Paraglomus)
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• Also in 2001, Schüssler et al. Re-evaluated the
  higher taxonomic ranks and decided that the AMF
  were fundamentally different than other fungi at
  the level of division. Hence they removed these
  fungi from the Zygomycota and erected a new
  taxon, the Glomeromycota. This contained 4 orders
  and 6 families.
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• Archaeosporales (Archaeosporaceae,
  Geosiphonaceae)
• Paraglomales (Paraglomeraceae)
• Diversisporales (Acaulosporaceae,
  Gigasporaceae and Diversisporaceae)
• Glomerales (Glomaceae A, B)
• Corrected form of earlier taxon
•  
• Note that the Diversisporaceae includes some
  former Glomus spp. to be transferred to
  Diversispora gen.nov. and that the Glomaceae was
  recognised to be polyphyletic.
•  

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Latest News

• 2004 New genus and family in the Diversisporales
  described both by
• Oehl Sieverding as Pacispora (in Pacisporaceae)
• and Walker et al. As Gerdmannia (Gerdmanniaceae)
• Former takes precedence by a matter of days!

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Controversy 1

• The molecular results used to create these new
  groups based on rRNA genes (ITS, SSU or LSU) but
  these are multi-copy and highly variable within
  spores.
• How do we validate with evidence from other
  genes?
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• e.g. ß-tubulin supports Glomeromycota but links
  them to Chytridiomycota.
• H-ATPase is not useful phylogenetically.
  (Corradi et al., 2004).

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Controversy 2

• How reliable is sequence information?
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• In all cases, contaminant sequences or
  mis-identified EMBL deposits have caused
  artefacts, hence there is the potentaial for
  errors to be made using unvalidated sequences.
•