noncellular holdfast, whereas the remaining
orders are saprobes, ectomycorrhizal, or haus-
torial or nonhaustorial parasites of animals or
plants(Benny 2009 , 2012 ; Benny et al. 2001 ;
Lichtwardt 1986 ; Lichtwardt et al. 2001 ). Taxa
of the Asellariales and Harpellales can be
reviewed on the trichomycete Web site (http://
http://www.nhm.ku.edu/~fungi/),,) and many of the
remaining orders are presented on the zygomy-
cete Web site (http://www.zygomycetes.org/).
Benjamin ( 1979 ) considered the mode of
nutrition an important taxonomic criterion at
the ordinal level and defined the following spe-
cialties: (1) saprobic or nonhaustorial (faculta-
tive) parasites (Basidiobolales, Mortierellales,
Mucorales, Kickxellales, some Entomophthor-
ales, and Endogonales); (2) haustorial (Dimargar-
itales, some Zoopagales) or nonhaustorial
parasites forming hyphal bodies (most Ento-
mophthorales) or coiled thalli (some Zoopagales);
and (3) ectomycorrhizae (some Endogonales).
The classification of zygomycotan fungi pre-
sented in the first edition (Benny 2001 ;Benny
et al. 2001 ) is based mainly on the morphology
of reproductive structures and the presence of
septa (Benjamin 1959 , 1979 ). The orders dis-
cussed by Benny ( 2001 )andBennyetal.( 2001 )
in the trichomycetes and zygomycetes are
revised here. Four of the orders presented in
the aforementioned chapters are now known
not to be zygomycotan fungi. These include pro-
tozoans (Amoebidales, Eccrinales) (Benny and
O’Donnell 2000 ;Cafaro 2005 ) or members of the
Glomeromycota (Geosiphonales, Glomerales—
as Glomales) (Schu ̈ssler et al. 2001 ; see Redecker
and Schu ̈ssler 2014 ). These deletions resulted in
the retention of nine orders (Asellariales, Basi-
diobolales, Dimargaritales, Endogonales, Ento-
mophthorales, Kickxellales, Mortierellales,
Mucorales, Zoopagales), and a tenth order was
described recently (Neozygitales; Humber
2012b). Phylogenetic studies resulted in the
description of one phylum, Entomophthoromy-
cota, and four subphyla, Kickxellomycotina,
Mortierellomycotina, Mucoromycotina, and
Zoopagomycotina, for these orders (Hibbett
et al. 2007 ;Hoffmannetal. 2011 ; Humber
2012b) as discussed subsequently.
II. Occurrence and Distribution
The members of Zygomycota are more or less
cosmopolitan, subsist on soluble nutrients,
and utilize a remarkable spectrum of
substrates. The most common sources of
Mucorales, Dimargaritales, Kickxellales, some
Zoopagales (Helicocephalidaceae, Piptocepha-
lidaceae, Sigmoideomycetaceae), and a few
genera of Entomophthorales (Basidiobolus,
Conidiobolus) are dung and soil.Many zygo-
mycetes can be isolated from soil, but the same
species can often be found on dung or other
organic material. A few taxa (e.g.,Hesseltinella,
Zygorhynchus) are found only in soil.
Pilobolusspecies (Grove 1934 ) are obligate
coprophiles. The other species found on dung are
not obligate coprophiles, but many of these fungi
usually are not isolated from other substrates.
Herbivore dung, especially from horses or cows,
is the most reliable source forPilobolusspp. The
dung of small, omnivorous rats and mice is often
the best source of the merosporangiferous
Mucorales [fungi now in Mucorales (Syncepha-
lastraceae), Kickxellales, Dimargaritales, and
Zoopagales (Piptocephaladiaceae)] (Benjamin
1959 ) and many other taxa in Mucorales.
Fungi in Endogonales, as currently circum-
scribed (Morton and Benny 1990 ), produce
zygospores with apposed suspensors in yellow to
orange sporocarps that are formed on or in the
soil or on organic debris such as leaves or wood.
Some species are ectomycorrhizal, but others are
saprobes. Members of Endogonales are infre-
quently collected but may occur worldwide.
Entomophthoralean fungi can be found in
virtually all temperate and tropical parts of the
world and are most commonly encountered as
pathogens of a very wide range of insects and
some phytophagous mites. The insects most
commonly affected by entomophthoralean
pathogens worldwide are aphids (Homoptera:
Aphididae) and a variety of lepidopterans
(mostly moths from many families), adult flies,
and grasshoppers and locusts (Orthoptera: Acri-
didae). A much smaller set of genera and species
attacks soil invertebrates such as nematodes.210 G.L. Benny et al.