Book of Abstracts (PDF) - International Mycological Association

IMC7 Tuesday August 13th Lectures
contain both lichenized and non-lichenized species. Here
we report a phylogenetic-comparative analysis of RPB2,
and the small and large subunit of the nuclear rRNA genes
from about 60 species representing about 75% of the
species diversity of the Ascomycota, a phylum that
includes > 98% of known lichenized fungal species. Using
a Bayesian phylogenetic tree sampling methodology,
combined with a statistical model of trait evolution, we
take into account uncertainty about the phylogenetic tree
and ancestral state reconstructions. Our results, based upon
a sample of 19,900 phylogenetic trees, show that lichens
evolved earlier than believed, and that gains of
lichenization have been infrequent during Ascomycota
evolution, but have been followed by multiple independent
losses of the lichen symbiosis. As a consequence, major
Ascomycota lineages (Ascosphaerales, Eurotiales,
Onygenales and Chaetothyriales) of exclusively nonlichen-forming
species are derived from lichen-forming
ancestors.
108 - Evolution of interkingdom host-jumping of
Cordyceps and the Clavicipitaceae
J.W. Spatafora * & G.-H. Sung
Oregon State University, Dept. of Botany and Plant
Pathology, 2082 Cordley Hall, Corvallis, OR 97331-2902,
U.S.A. - E-mail: spatafoj@bcc.orst.edu
The genus Cordyceps includes over 300 described species
of fungi that are pathogens of arthropods and fungi. It is a
member of the Clavicipitaceae (Ascomycota, Hypocreales)
which also includes symbionts of plants, mainly of the
Poaceae. Current subfamilial classification of the
Clavicipitaceae comprises the Clavicipitoideae, which
includes all of the grass symbionts, and the
Cordycipitoideae, which includes all of the pathogens of
arthropods and fungi. This represents an evolutionary
hypothesis that implicitly assumes inter-Kingdom host
jumps are rare and irreversible. To test this hypothesis we
initiated a molecular phylogenetic study of the
Clavicipitaceae with a particular emphasis on Cordyceps.
We have assembled a four-gene region dataset that
includes data from the nuclear SSU and LSU rDNA, betatubulin,
and elongation factor 1-alpha for 75 taxa.
Phylogenetic analyses reject the monophyly of Cordyceps
and the Cordycipitoideae and do not support host jumps as
being rare and irreversible. Three clades of clavicipitaceous
fungi, which all contained pathogens of animals and fungi,
were resolved in these analyses. Pathogen of animals is
resolved as the primitive symbiosis for the Clavicipitaceae
with a single jump to the Poaceae that was most likely
followed by a reversal to animals. Multiple jumps have
occurred from animals to fungi with at least one reversal to
animals. Character coding of host affiliation and testing
character state reconstructions will be discussed.
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Book of Abstracts
109 - Molecular phylogenetics and breeding systems in
the ascomycete fungi
M.L. Berbee
Department of Botany, University of British Columbia,
Vancouver BC V6T 1Z4, Canada. - E-mail:
berbee@interchange.ubc.ca
By a combination of phylogenetic approaches, we are
studying the evolution of breeding systems among fungi in
the Ascomycota. Within the family Pleosporaceae,
combined data from the glyceraldehyde-3-phosphate
dehydrogenase gene and ribosomal ITS regions provide
good resolution. Our phylogenetic analysis shows that the
'asexual' species and the selfing species are nested among
outcrossing sexual species, indicating that outcrossing
sexuality was the ancestral condition for the family. In
sexual filamentous ascomycetes, opposite mating type
information at the MAT1 locus regulates mating and the
opposite mating type genes each have a clonal, nonrecombining
phylogenetic history. Many species in the
Pleosporaceae have no known sexual states, but where
tested, these supposedly asexual fungi have intact,
functional mating type genes. We used PCR to amplify and
sequence fragments of the opposite mating type genes from
supposedly asexual species in the genus Alternaria, in the
Pleosporaceae. Each haploid fungal isolate had just one
mating type, but both mating types were present in each
species. We sequenced the ribosomal ITS regions for
isolates of opposite mating types, for three asexual species
and four known related sexual species. Analysis of the
probability of substitution patterns indicated that, if
sexuality had been lost, it was lost after the most recent ITS
substitutions had evolved in each species.
110 - Trends in morphological evolution in
homobasidiomycetes
D.S. Hibbett * & M. Binder
Biology Department, Clark University, Worcester MA
01610, U.S.A. - E-mail: dhibbett@black.clarku.edu
Homobasidiomycetes display an incredible diversity of
fruiting body forms, ranging from simple corticioid forms,
which lie flat on their substrates, to elaborate,
developmentally integrated forms, such as stinkhorns.
More than half of all described homobasidiomycetes have
pileate-stipitate fruiting bodies, with gills or other
configurations of the hymenophore. A functional (if not
phylogenetic) distinction can be made between
gasteromycetes, which lack ballistospory and produce
spores internally, and hymenomycetes, which retain
ballistospory and produce spores externally. Much of the
research in higher-level homobasidiomycete systematics in
the last century has focused on tracing patterns of evolution
in fruiting body forms, and has revealed extensive
convergence. Our recent analyses concern trends in the
evolution of fruiting body morphology. Examples of the