Systematics and Evolution, Part A The Mycota

genera, and approximately 180 species. It is
likely that many additional species, genera,
and higher taxa remain to be discovered and
described. Figure7.3summarizes the results
from a Bayesian rDNA (SSU+5.8S+LSU) phy-
logeny, including 45 gene sequences from the
Blastocladiomycota representing 4 of the 5
families (Porter et al. 2011 ). Here we review
the phylogenetic placement of the various
families, the evidence of monophyly of genera,
and the morphological characters that separate
the various genera.
The Blastocladiaceae Petersen 1909 cur-
rently comprises five genera:AllomycesButler
1911 , Blastocladia, Microallomyces Emerson
and Robertson 1974 ,BlastocladiellaMatthews
1937 , andBlastocladiopsisSparrow 1950 (Kar-
ling 1977 ). Genera can be separated on the basis

of thallus organization.Allomycesis the only

genus that displays truly indeterminate growth

as a mycelium with septa, andMicroallomyces

is similar toAllomycesbut smaller in stature

and lacking pseudosepta. Members ofBlasto-

cladiatypically have a single trunklike basal

cell, with septations only at reproductive

organs. The poorly knownBlastocladiopsisis

distinguished fromBlastocladiaon the basis of

an unpitted, loose resting sporangium. In

Fig.7.3, strains fromAllomyces,Blastocladia,

andMicroallomycesform a clade, three strains

ofBlastocladiellaandBlastocladiella emersonii

Cantino and Hyatt 1953 cluster separately, and

the genusBlastocladiopsishas yet to be placed

in a molecular phylogeny. ThoughAllomyces

forms a clade, Porter et al. ( 2011 ) showed that

these taxa do not necessarily group according

Paraphysoderma sedebokerense(1)

Allomyces(13) +

Blastocladia(2) +

Microallomyces(1)

Catenaria spinosa(3)

Catenaria s.s.(7) +

Catenophlyctis(1)

Blastocladiella(3) +

Blastocladiella emersonii(1)

Coelomomyces(4) +

Coelomycidium(2)

Physoderma(4) +

Urophlyctis(3)

50 changes

Blastocladiaceae

Catenariaceae

Blastocladiaceae

Coelomomycetaceae

Physodermataceae

Blastocladiomycota

Families (Karling,1977)

rDNA operon clades and

lineages (Porter et al., 2011)

Fig. 7.3Schematic phylogeny of Blastocladiomycota
based on rRNA operon sequences (Porter et al. 2011 )
with taxonomic classifications from Karling ( 1977 ).

Numbers following generic names: number of

sequences included

Blastocladiomycota 185