Biologie der Interaktion zwischen Koleopteren und agaricoiden Basidiomyzeten

The aim of this study was to analyze mechanisms and ecological relationships between Coleoptera and basidiocarps of agarics. Therefore, field experiments as well as laboratory experiments were conducted in basidiocarps of Megacollybia platyphylla and Marasmius alliaceus served as model systems. Basidiocarps of both mushrooms were picked up in three consecutive years in two different natural forest preserve reservations and in one economic forest area incidentally. Due to their ephemerality, their rapid transience, and their discontinuous temporal and spatial occurrence, basidiocarps of agarics are regarded as exceptionally unstable microhabitats. Therefore, the agaricoid basidiocarps seem to be inapt for the development of specialized and specific associations with insects. The present field studies, however, revealed that the fructification of Megacollybia is characterized by broad temporal and spatial pattern of occurrence. Marasmius alliaceus resembles this type of fructification. These results suggest that in contrast to other agaricoid mushrooms, basidiocarps of Megacollybia platyphylla and Marasmius alliaceus may serve as appropriate habitat resources for insects. This assumption was supported by colonization data. In particular the two mycophagous staphylinids Gyrophaena joyioides and G. gentilis showed high dominance and continuity values at Megacollybia platyphylla and Marasmius alliaceus basidiocarps indicating specificity to these species. Moreover, the present study revealed that basidiocarps of these two species serve as aggregation centers, mating arenas, food source, for oviposition, and as refuge for larval development. Furthermore, the study uncovered that both G. joyioides and G. gentilis have an extremely shortened larval developmental period though using different breeding strategies. These breeding strategies are interpreted as specific adaptations to the ephemeral microhabitats. Laboratory experiments established another adaptation mechanism of insects to their specific habitat niche. Observation of settlement and colonization showed that Gyrophaena use mushrooms of different developmental phases in a different way. Based on this data, a meta-population concept was developed. This concept includes staphylinid migration behavior and mushroom habitat proposition to model the dynamic proceedings during occupation of this particular habitat niche. It is assumed that the represented adaptive mechanisms and concepts constitute elementary features to ensure effective and continual colonization of the ephemeral agaricoid basidiocarps by Gyrophaena. Another aim of the study was the ecological characterization of the association between basidiocarps of agarics and settling Coleoptera. Obviously, Coleoptera benefit from settling at Megacollybia platyphylla and Marasmius alliaceus basidiocarps by feeding the reproductive units of the mushrooms. As a consequence, however, they harm the mushrooms. To investigate whether there is any benefit on the side of the mushrooms, a potential spore dispersal contribution by the basidiocarp settling insects was assessed. Despite a high dispersal potential of mushroom spores in the control organisms Armillaria mellea agg., Pholiota aurivella, Pholiota squarrosa, and inoculum dissemination of ubiquitous fungi, saprobiontic and pathogenic fungi of plants, entomopathogenic fungi, and particularly mycotrophic fungi by basidiocarp colonizing insects, however, there was no evidence forinsect dispersal of basidiospores within the specific Gyrophaena-Megacollybia platyphylla/Marasmius alliaceus-association. Thus, these mushrooms seem not to benefit from specific association. In contrast, due to impairment of basidiospore feeding and increased infestation with mycoparasitic fungi, they are impaired by colonization. The Gyrophaena on the other hand profit by the specific association. In conclusion, specific Gyrophaena-Megacollybia platyphylla/Marasmius alliaceus-association must be classified as a system of exploitation.