uncultured and uninvestigated zoopagalean fungi,
the monophyly of the Zoopagales remains an open
question.
In contrast to the present phylogenetic study, RPB1
protein sequence-based analyses placed the Dimar-
garitales in a position basal to the Kickxellales-
Harpellales (Tanabe et al 2004). A Dimargaritales +
Kickxellales + Harpellales (i.e. the DKH clade)
relationship receives morphological support as well
because all three orders produce regularly formed
septa with a lenticular cavity. Conversely, support for
a Dimargaritales + Zoopagales sister group relation-
ship may be reflected in the putative synapomorphic
production of common parasitic organs such as
haustoria. The possible significance of parasitism in
the evolution of the Zoopagales with members of the
‘‘DKH’’ cluster requires further study.
Entomophthorales + Basidiobolus.—Entomophthor-
ales literally translates to ‘‘insect destroyers’’, with the
common housefly infected with Entomophthora mus-
cae on a window pane being the most widely used
example (see tree F
IG
. 1, also F
IGS
. 5–24 in Alexo-
poulos et al 1996). Many species are saprophytic;
however some facultative or obligate pathogens show
potential for the biological control of pest insects
(Carruthers and Hural 1990). Some species of
Basidiobolus and Conidiobolus cause serious mycoses
in animals including humans (de Hoog et al 2000).
Thaxter (1888) produced the first monographic
treatment of Entomophthorales, and Underwood
(1899) was the first to adopt the ordinal name.
Zygospores, coenocytic thalli and repeated conidial
discharge distinguish the Entomophthorales (Benny
et al 2001). Entomophthoralean asexual spores are
different from other Zygomycota ontogenetically
because they are holoblastic conidia that lack
a sporangiospore wall. In addition to their commonly
observed forcibly discharged conidia some species
also form secondary capilliconidia (Benny et al 2001,
F
IGS
. 32–35), similar to those formed by some
members of the Zoopagales (Blackwell and Malloch
1991). Secondary capilliconidia (insect dispersed)
provide an alternative dispersal mechanism (Ben-
Ze’ev and Kenneth 1982, Humber 1981, King and
Humber 1981). Genera of Entomophthorales have
been distinguished phenotypically by conidial and
conidiophore features, mode of discharge and gen-
eral habit and host range (Benny et al 2001).
The Entomophthorales have been classified in up
to six families and 22 genera (Kirk et al 2001).
Humber’s (1989) classification, which included six
families (i.e. Ancylistaceae, Basidioboloaceae, Com-
pletoriaceae, Entomophthoraceae, Meristacraceae
and Neozygitaceae), will require further data to assess
its monophyly (F
IG
. 1). In the present rDNA-based
phylogenetic analysis three clades of Entomophthor-
ales were resolved: (i) Basidiobolus with an unde-
scribed snake pathogen (listed in GenBank as
Schizangiella serpentis sp. nov. Humber); (ii) the core
Entomophthorales including Conidiobolus; and (iii)
Neozygites with the Dimargaritales. Similarly the SSU
phylogeny of Jensen et al (1998) recovered the
‘‘core’’ Entomophthorales as a monophyletic group,
excluding Basidiobolus, which was nested within the
Chytridiales, as noted initially by Nagahama et al
(1995).
Conidial release of Basidiobolus is by a ‘‘rocket
mechanism’’ with its conidium remaining intact and
with the upper part of the conidiophore. The rocket
mechanism contrasts with the core Entomophthora-
les described as having a ‘‘rounding-up’’ mechanism
or ‘‘papillar eversion’’ ( Jensen et al 1998). Although
a separate order, the Basidiobolales, has been pro-
posed for Basidiobolus spp. (Cavalier-Smith 1998)
concerns about LBA ( James et al 2000) suggest that
this proposal needs to be evaluated critically based on
multilocus analyses including slowly evolving protein
coding sequences. Morphological characters, such as
a large nucleus and spindle pole body with microtu-
bular structure, however do distinguish Basidiobolus
when compared to Entomophthorales (see below,
Chytridiomycota). Careful evaluation also is suggested
for species of Neozygites, obligate parasites of mites
and insects (Ben-Ze’ev et al 1987, Humber 1989,
Keller 1997) clustered in a putatively ‘‘fast evolving’’
Dimargaritales clade in this study (F
IG
. 1).
Missing Zygomycota.— Asellariales. This is a small
order of arthropod gut fungi (Trichomycetes) with
two recognized genera, Asellaria and Orchesellaria (in
isopods and springtails, respectively), and a putative
third member, Baltomyces, also in isopods (Cafaro
1999). The members of the order are characterized by
branched thalli and arthrospores (F
IG
. 3J). Taxonomy
hinges on basal cell morphology (Valle 2006).
Ultrastructurally septa are incomplete with a lenticular
cavity and a plug (Saikawa et al 1997), similar to those
of the DKH clade. Sexual reproduction is unknown
and none have been cultured. Sequences of Asellari-
ales must be obtained to test the hypothesis of a close
relationship between the Asellariales and Harpellales
based on morphological data. Such an analysis also
will be essential to help resolve the basal branches in
the Zygomycota phylogeny.
Amoebidiales + Eccrinales.— Phylogenetic analyses of
these orders (previously misclassified as Trichomy-
cetes) including results of the present study (F
IG
. 1),
indicate that both are monophyletic and are sister
taxa (Benny and O’Donnell 2000, Cafaro 2005). They
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M
YCOLOGIA