Response of the chydorid faunas to rapid climatic changes in four alpine lakes at different altitudes

The subfossil assemblages of Chydoridae from Late Glacial/Preboreal sediments of four sites from 603 m to 2290 m asl were analysed to trace the community response to rapid climatic warming that occurred at this period of time. In each site, distinct signals at the Younger Dryas/Preboreal boundary were recorded by density of remains, species diversity or community composition. However, responses varied considerably among the sites. This variation was attributed to the situation that the chydorid community structure is determined not only by temporal (Younger Dryas/Preboreal boundary) and spatial (among the sites) temperature gradients, but also by the specific local ecological conditions at the sites. In some species the classification with respect to cold tolerance should be reconsidered.