Mechanisms, phenotypic plasticity and genotypic determination of thermal tolerance and related properties in Daphnia and Leptodora kindtii:: consequences for temperature impacts on food web interactions

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Global warming may have far-reaching effects on aquatic ecosystems through direct or indirect effects on the physiological systems of its members. The genus Daphnia plays a central role in the ecology of almost all standing freshwater, and Chaoborus larvae are prominent invertebrate predators of Daphnia. For a mechanistic understanding of thermal effects on Daphnia and Chaoborus larvae, field data analysis, physiological and biochemical investigations and retrospective studies will be brought together: investigation of the seasonal changes of phenotypic acclimatization as well as of clonal structure and clone-specific thermal tolerance will allow to evaluate future ecological consequences of global warming. The physiological and biochemical mechanisms and the degree of thermal tolerance as well as traits related to physiological fitness will be analysed and accordingly, costs or benefits of a changed thermal performance will be assessed. These results will be linked with the environmental conditions during the seasons. An understanding of the role of temperature for the performance and fitness of Daphnia and Chaoborus will allow to predict firstly, if specifically this prey-predator pair may grow apart from each other at global warming due to a mismatch of their thermal performances and capacities, and secondly, how the general properties or strategies of Daphnia at different temperatures will match the temporal abundance of food resources. A general view on Daphnia will be derived from the comparison of differently thermally adapted, yet closely related clones and species.