alistic mycobionts of plant roots in terrestrial
ecosystems, some species seem to have a sapro-
trophic lifestyle (Craterocolla,Efibulobasidium).
SinceP. indicaand members of the morphospe-
ciesSerendipita vermifera grow axenically in
standard media, it can be assumed that many,
if not all, species of Sebacinales Group B (see
below) have saprotrophic abilities.
Systematics: the monophyly of the Sebaci-
nales has been demonstrated in molecular phy-
logenetic analyses (Weiß and Oberwinkler
2001 ; Weiß et al.2004b). All comprehensive
analyses of phylogenetic relationships within
Sebacinales have been based on nuclear-
encoded rRNA genes, including the internal
transcribed spacers (ITS) and partial large sub-
unit (nuc-lsu) regions. Most of the sequences
analyzed have come from environmental
sources; multilocus data derived from fruiting
bodies or cultures are needed to solidify the
systematics of Sebacinales. The available
molecular phylogenetic analyses indicate that
Sebacinales is divided into two monophyletic
subgroups, informally known as Group A and
Group B.
Group A: Species forming macroscopically visible basi-
diomes have only been reported fromGroup A.The
types of interactions with plant roots are not uniformly
distributed over Groups A and B; most of the reported
taxa known to be involved in ectomycorrhizae belong to
Group A, whereas sebacinalean mycobionts of ericoid
mycorrhizae have only been reported from Group B.
Group B: The vast majority ofGroup Btaxa are
known only from environmental sequences.S. vermi-
ferais the only known teleomorph in this group, yet it
has been shown that this morphospecies is in fact a
broad complex of cryptic species (Weiß et al.2004b), all
of which may lack macroscopic basidiomes, that pro-
duce exceptionally long vermiform basidiospores and
are very poor in distinctive microscopic characters. It is
possible that all teleomorphic species in Sebacinales
Group B belong to this morphospecies and that the
anamorphic genusPiriformospora, with two currently
described species, evolved within this group from aS.
vermifera-like ancestor that lost the ability to repro-
duce sexually.
C. Auriculariales
Overview: Auriculariales in its current concept
includes ca. 30 genera with ca. 200 described
species (Kirk et al. 2008 ; Weiß et al.2004a). It
comprises wood-decaying fungi with a broad
spectrum of basidiome shapes, including
effused (Exidiopsis,Basidiodendron), effuso-
reflex (Eichleriella), odontoid (Stypella), hyd-
noid (Pseudohydnum)(Fig.14.3c), and infundi-
buliform (Tremiscus) basidiomes. Basidiomes of
some species even have a poroid or daedaleoid
habit (Elmerina[includingAporpiumandPro-
todaedalea], Protomerulius) (Zhou and Dai
2013 ). All known species cause a white rot,
some are regularly found on buried wood
(Tremiscus helvelloides). Key characters of the
Auriculariales include dolipores with continu-
ous parenthesomes and the ability of basidios-
pores to form ballistoconidia (secondary
basidiospores). With the exception ofHyaloria
pilacre, all species are ballistosporic.
Most of the known species in the Auricular-
iales have longitudinally septate basidia, but
there are also species with transversely (Auri-
cularia) or obliquely septate (Patouillardina)
and even nonseptate (Oliveonia) or apically
partially septate (Tremellodendropsis) basidia.
In some genera (e.g.,Myxarium,Protodontia,
Pseudohydnum,Pseudomerulius,Stypella,Tre-
miscus), basidia have a plasma-devoid “stalk”
(myxarioid, sphaeropedunculate basidia),
which probably represents a taxonomically rel-
evant character (Weiß and Oberwinkler 2001 ;
Wells and Bandoni 2001 ). An explanation of
this peculiar morphology was given by Bandoni
( 1984 ), who interpreted the basidial compart-
ments themselves as intrabasidial meiotic pro-
ducts (endospores) that in germination break
the outer basidial wall and develop a single
conidium, the “basidiospore” in common ter-
minology. In the myxarioid members of the
Auriculariales the endospores do not fill the
complete basidium but leave the characteristic
stalk.
Many investigated species show clamps
with characteristic retrorse projections (so-
called spurred clamps) (Bandoni and Wells
1992 ). Another characteristic microscopic fea-
ture reported from many species of Auricular-
iales is the ability of basidiospores to produce
mostly crescent-shaped microconidia on short
sterigmalike projections (Ingold 1982a, b).
Little is known about other anamorphs in
Auriculariales. From recent reports about
sporodochial, synnematous, bulbilliferous, and
possibly also pycnidial examples in this group390 D.S. Hibbett et al.