2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

harshest end of the gradient, and abiotic conditions limiting the better competitor, P.
reticulata, to the mildest end of the gradient. Interestingly, this trade-off was also
observed at the family level in P. reticulata. Families more tolerant to salinity are
worst competitors than less tolerant ones. Thus, selection to increase stress
tolerance in this species will come at the expense of a reduction on competitive
ability. We conclude that the downstream limit to the distribution of P. reticulata is
driven by salinity, and is evolutionarily stable; and that the upstream limit to the
distribution of P. picta is driven by competitive exclusion, and is potentially nonstable.
����59 Monika Trienens
Chemical defense and reciprocal benefits mediate trophic interactions of
Drosophila melanogaster with microfungi
Authors: Monika Trienens 1 , Marko Rohlfs 1
Affiliation: 1 Georg-August-University Göttingen
Development of Drosophila melanogaster is linked to decaying fruit. Here, microfungi
transmitted by adults to breeding sites crucially affect larval development as dietary
mutualists (e.g., yeasts) and antagonists (e.g, moulds). The mechanisms underlying
these contrasting patterns of insect-microfungal interactions are poorly understood.
Despite strong feeding pressure on yeast, Saccharomyces cerevisiae, larval foraging
activity provided, in an insect density-dependent manner, a net benefit to the growth
of yeast cell populations. In contrast, the toxin-producing filamentous fungus,
Aspergillus nidulans, did not support larval development; yet, a chemical deficient A.
nidulans mutant turned out to serve as a suitable, but rapidly diminishing dietary
resource for D. melanogaster larvae. In addition to its dietary function for D.
melanogaster larvae, we found yeast to suppress mould growth by means of volatile
emission. Moreover, D. melanogaster females prefer to lay eggs on yeast-infested
patches but avoid the ones heavily infested with moulds. While the combined
positive effects of D. melanogaster egg-laying and larval foraging behaviour on yeast
population growth support the idea of an insect-fungus mutualism, chemical
defence, filamentous growth, and antagonism with Drosophila-transmitted yeasts
represent a critical combination of mould properties that foster evolution of insectfungus
antagonisms.
����60 Martina Weiss
Population structure of Gammarus fossarum in a central German low mountain
range (Hochsauerland)
Authors: Martina Weiss 1 , Marcus Liebert 1 , Jan Macher 1 , Ralph Tollrian 1 , Florian
Leese 1
Affiliation: 1 Department of Animal Ecology, Evolution and Biodiversity: Ruhr University
Bochum
Gene flow between populations of freshwater organisms is affected by extrinsic and
intrinsic factors. The former encompass geographical distance, geological relief and
hydrological barriers, whereas intrinsic factors include the ability to disperse actively.
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