Book of Abstracts (PDF) - International Mycological Association

IMC7 Thursday August 15th Lectures
318 - The natural abundance of 15 N in mat-forming
lichens
C.J. Ellis 1* , P.D. Crittenden 1 & C.M. Scrimgeour 2
1 School of Life and Environmental Sciences, University of
Nottingham, Nottingham, NG7 2RD, U.K. - 2 Scottish Crop
Research Institute, Invergowrie, Dundee, DD2 5DA, U.K. -
E-mail: christopher.ellis@nottingham.ac.uk
Natural abundance of 15 N and [N] was studied in thalli of
mat-forming lichens collected from tundra and heathland
sites in the Northern and Southern Hemispheres. The study
includes samples of British Cladonia portentosa from sites
in regions of high and low N-loading and in heathland
growing on peat and independently of the soil substratum,
in a canopy of prostrate gorse. In the mat-forming lichens
examined, a non-random pattern in [N] and δ 15 N was
characterised by a minimum in δ 15 N, which occurred most
frequently at 40-60 mm below the thallus apex. [N]
increased above this point, towards the apex, though
remained invariably low towards the thallus base. We
discuss the significance of the pattern in [N] and δ 15 N for
current theories describing the uptake and recycling of
nitrogen by mat-forming lichens in oligotrophic habitats.
Our data are incompatible with the suggested uptake of soil
organic nitrogen depleted in 15 N, though are consistent with
possible internal recycling and the development of a
structural necromass. The study emphasises the internal
fractionation of nitrogen isotopes and provides a caveat
against the assumption that values of δ 15 N provide an
unequivocal indicator of source-sink relationships in
nitrogen cycling.
319 - Role of environmental conditions and birch tree
genotype in endophyte-herbivore interactions
K. Saikkonen
University of Turku, Section of Ecology, Department of
Biology, 20014 Turku, Finland. - E-mail: karisaik@utu.fi
We compared phenotypic and genetic frequency
correlations for two endophytic fungal genera (Fusicladium
and Melanconium) and bich rust (Melampsoridium
betulinum) with the performance of six invertebrate
herbivores growing on the same half-sib progenies of
mountain birches (Betula pubescens ssp. czerepanovii) in
two environments over a 3-year period. We found little
support for causal association between fungal frequencies
and performance of herbivore species. Instead, genetic
correlations, particularly between autumnal moth (Epirrita
autumnata) and birch rust, suggest that herbivore
performance may be affected by (1) genetic differences in
plant quality for fungi and herbivores, or (2) genetic
differences in responses to environmental conditions.
Genetic analysis (RAMS-PCR) of Venturia ditricha
(anamorph Fusicladium betulae) revealed that (1) host
genotypes and environment influence the probability of
infection by particular endophyte genotypes, (2) genetic
variation correlated negatively with infection frequencies
of the fungus, and (3) the susceptibility of the host to a
particular endophyte genotype may change when
environmental conditions are changed (environment-host
genotype interaction). Our results propose that the
seemingly direct interactions between herbivores and fungi
may actually indicate genetic differences in plant quality
for fungi and herbivores or responses to environmental
conditions.
320 - Specificity of fungal-algal interactions on leaves
M. Grube 1* , E. Baloch 1 & R. Luecking 2
1 Institute of Botany, Holteigase 6, A-8010 Graz, Austria. -
2 The Field Museum of Natural History, 1400 South Lake
Shore Drive, Illinois 60605-2496, U.S.A. - E-mail:
martin.grube@uni-graz.at
Several types of algae are adapted to the growth on living
leaves, coccoid green algae and members of
Trentepohliales being most common and also serving as
photobionts of lichen-forming fungi. Initials of these
lichens need to form composite thalli with appropriate
algae in a relatively short time. Therefore, particular
strategies are pursued to ensure efficient dispersal and
colonialization of leaves. Specific growth patterns of
trentepohlioid algae, found in both lichenized and nonlichenized
forms, suggest that foliicolous mycobionts have
a high specificity for their photobionts. Adjacent freeliving
Phycopeltis colonies belonging to different
morphotypes are not accepted as photobionts by the same
fungus. Different ecological preferences of photobionts
apparently shape the diversity of foliicolous lichens found
in a given microhabitat. A particular strategy regarding
photobiont selection of lichens is found in lichenized,
foliicolous species of Chroodiscus, which grow
facultatively parasitic on lichens of the genus Porina. C.
australiensis and C. coccineus show a high degree of host
specificity: C. australiensis parasitizes Porina mirabilis,
whereas C. coccineus is specifically found on P.
subepiphylla. In genera of lichens, which include both
lichenized and non-lichenized, lichenicolous species (e.g.
Arthonia), the latter take advantage of the host photobionts.
321 - Fungal endophytes in a neotropical forest:
ecological, systematic, and physiological insights
A.E. Arnold 1* , L.C. Mejía 2 , E. Rojas 2 , D.A. Kyllo 2 & E.A.
Herre 2
1 University of Arizona, Department of Ecology and
Evolutionary Biology, 1041 E. Lowell, BSW 310, Tucson,
AZ 85721, U.S.A. - 2 Smithsonian Tropical Research
Institute, Apartado 2072, Balboa, Panama. - E-mail:
betsya@email.arizona.edu
Fungal endophytes associated with woody angiosperms are
abundant and diverse; yet especially in tropical forests,
Book of Abstracts 101