Systematics and Evolution, Part A The Mycota

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2007 , 2011 , 2012 ; Miki et al. 2011 ; Sime-Ngando
et al. 2011 ).
This chapter updates Barr’s ( 2001 ) review
of zoosporic fungi, with an emphasis on how
molecular and ultrastructural phylogenetic
analyses have revolutionized the taxonomy of
zoosporic fungi. As we rapidly learn more about
the biology, diversity, and global distribution of
zoosporic fungi, we are revising their systemat-
ics, which, as a consequence, is in a state of flux
(Powell and Letcher 2012 ). The phylum Chytri-
diomycota as circumscribed by Barr ( 2001 ) has
now been separated into three additional
validly published phyla: Blastocladiomycota
(James et al.2006b), Monoblepharidomycota
(Doweld 2001 ), and Neocallimastigomycota
(Hibbett et al. 2007 ), each circumscribing a
monophyletic lineage (Fig. 6.1, Table 6.1).
Moreover,Rozellaspecies, once classified in
the Chytridiomycota, are now amalgamated
with filose pseudopodiate (pseudociliate)
organisms in the phylum Cryptomycota
(Jones et al. 2011 ; Karpov et al. 2013 ).Blasto-
cladiomycotais commonly placed as the sister
group of zygomycetous fungi (Fig.6.1) and


diverges from other groups of zoosporic fungi
[James et al.2006b; see James et al. ( 2014 )].
However, in different analyses, other place-
ments may be found (Ebersberger et al. 2012 ;
Sekimoto et al. 2011 ). We summarize progress
in the systematics of Chytridiomycota(chy-
trids),Monoblepharidomycota(monoblephs),
and Neocallimastigomycota (neocallimasti-
gos).

II. Occurrence and Dispersal


Zoosporic fungi are common members of
aquatic and soil microbial communities and
can be isolated from or detected on leaf litter
and tree-canopy detritus (Bandoni and Barr
1976 ; Bills et al. 2004 ; Letcher and Powell
2001 ,2002b; Longcore 2005 ; Nikolcheva and
Barlocher 2004 ; Powell 1993 ; Shearer et al.
2004 ). Chytrids are microscopic, and their
thalli may be observed from environmental
samples of algae, other hosts, or organic sub-
strates.Monoblephstypically occur on totally
submerged waterlogged twigs, decorticated

Fig. 6.1Phylogenetic hypothesis for zoosporic fungi
based on James et al. (2006b). Four phyla have been
formally circumscribed: Blastocladiomycota, Chytri-
diomycota, Monoblepharidomycota, and Neocallimas-


tigomycota. The phylum Cryptomycota, which is
considered either a fungal or protistian phylum,
includes the zoosporic genusRozellaspp., earlier clas-
sified in the Chytridiomycota

142 M.J. Powell and P.M. Letcher

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