Book of Abstracts (PDF) - International Mycological Association

IMC7 Friday August 16th Lectures
having two names confuses non-mycologists and can cause
problems in communication. There has always been
discomfort at the existence of an artificial taxonomic
system for anamorphs that imperfectly parallels the
supposedly phylogenetic holomorphic system. Calls for the
abolition of dual nomenclature have become more frequent
with the advent of molecular systematics, which allows all
fungi to be included in a unified phylogeny irrespective of
the morphology expressed. Dual nomenclature for some
groups of fungi is governed by Article 59 of the
International Code of Botanical Nomenclature, but this
does not apply to all and no such provision exists for any
other kinds of organisms. We will argue for the eventual
rejection of formalized dual nomenclature and a major
revision of Article 59.
351 - Biogeography and species complexes in some
corticioid fungi
N. Hallenberg * & R.H. Nilsson
Botanical Institute, Box 461, SE-405 30 Gothenburg,
Sweden. - E-mail: nils.hallenberg@systbot.gu.se
Species diversity has by tradition been based on a
morphological species concept. As shown in numerous
studies such morpho-species among corticioid
basidiomycetes are frequently complex, consisting of
morphologically indistinguishable biological species.
Phylogenetic analyses based on ITS sequences support the
biological species concept. Moreover, from such analyses it
may be possible to estimate genetic divergence within and
between geographical regions as well as evolutionary
relationships between biological species. For a few species
an extensive sampling has been done, originating from
temperate areas around the world. From datasets in
Hyphoderma praetermissum and Hyphoderma setigerum it
is shown that representatives from some of the different
biological species have very wide distribution areas at
least. The different groups revealed in a complex are
distinctly separated in their sequence divergence but, on the
other hand, more closely related to each other than to
morphologically distinguished relatives. Homothallic
isolates group together with heterothallic ones, indicating
that homothallism must be looked upon as a life strategy
which repeatedly have come into existence within certain
populations.
352 - Genetic and molecular evidence for vicariance
events in the hymenomycetes
K.W. Hughes 1* , R.H. Petersen 1 & S.A. Redhead 2
1 Dept. of Botany, University of Tennessee, Knoxville, TN,
USA 37996-1100, U.S.A. - 2 Agriculture and Agri-Food
Canada, Ottawa ON K1A 0C6, Canada. - E-mail:
khughes@utk.edu
Many Northern Hemisphere basidiomycete fungi have
intercontinental distributions (North America, Europe and
Asia). For the taxa we have studied, most collections retain
the ability to interbreed in vitro throughout their
geographical range (e.g., Auriscalpium vulgare,
Flammulina velutipes, F. rossica, Panellus stypticus,
Lentinellus castoreus, Clavicorona pyxidata, Collybia
cookei, C. cirrhata and C. tuberosa). We have examined
the genetic relationships among collections of selected taxa
from widely separated geographical regions based on
ribosomal ITS DNA sequences. For Panellus stypticus,
Flammulina velutipes and F. rossica, the data suggest that
western NA and Asian populations are most closely
related, perhaps via Beringia. Eastern NA populations of
these species are clearly distinct but their origins are
obscure, perhaps derived from western NA populations,
perhaps from Europe. For Clavicorona pyxidata, the data
suggest that collections from eastern NA and Europe are
most closely related, possibly through a North Atlantic land
bridge open during the Eocene. For species with both
Northern and Southern Hemisphere distributions, migration
may have occurred via the Malaysian Archipelago
(Panellus stypticus) or via South and Central America
(possibly Lentinellus castoreus). The finding of distinct but
contaxic fungal populations across broad geographical
areas suggests that fungal species may be very old.
353 - Natural biogeography and movement by humans
of host-specialized forms in the Ceratocystis fimbriata
complex
T.C. Harrington * & C.J. Baker
Iowa State University, Department of Plant Pathology,
Ames, 50011, Iowa, U.S.A. - E-mail: tcharrin@iastate.edu
There is little morphological diversity but a wide range of
hosts in the wilt pathogen Ceratocystis fimbriata.
Sequences of rDNA and the MAT-2 gene have shown a
surprising amount of variation among more than 200
isolates studied. Phylogenetic analyses group all isolates
into three major geographic clades, each comprised of hostspecialized
lineages. The center of diversity of the complex
is found in the USA, and the North American clade (NAC)
includes lineages on Prunus, Quercus, Populus and Carya.
The Asian clade (AC) includes a Ficus lineage and a
Colocasia lineage. The Latin American clade (LAC)
appears indigenous from southeastern USA to South
America. The LAC has a wide range of hosts, many of
which are exotic crop plants, but it is less genetically
diverse and appears younger than either the AC or NAC.
Host specialization was demonstrated in LAC populations
on Ipomoea, Platanus, the family Araceae, Coffea,
Theobroma, Gmelina, Eucalyptus, and Mangifera. The
LAC appears to be comprised of relatively small and
geographically isolated populations in the process of hostspecialization
and speciation. Genetic isolation of LAC
populations may be due to limited geographic dispersal by
insects. However, there is genetic and historical evidence
for dissemination by humans of C. fimbriata strains on
plant materials: Colocasia (AC) to Hawaii, Populus (NAC)
to Poland, and LAC forms on Ipomoea to Asia, Syngonium
to Hawaii, Platanus to Europe, and Theobroma to Brazil.
Book of Abstracts 111