Abstracts (first author)
The evolutionary adaptive potential of Daphnia galeata in time and space
In the framework of global change research we aimed at estimating the impact of elevated water temperatures on an aquatic keystone species, the freshwater zooplankter Daphnia galeata. To quantify the evolutionary potential of the resident natural Daphnia populations, we performed experiments measuring variation in life-history traits under different temperatures. In a “resurrection ecology” approach, we sampled dormant egg banks of Daphnia galeata populations to obtain a representative sample of natural genetic diversity. We first compared locally adapted populations by sampling individuals from recent/superficial sediment layers, sampled along a latitudinal gradient from Norway to Italy. In a second experiment we used layers from different depths, comparing clones/populations from different time periods. After hatching and establishing clonal lineages in the laboratory, we performed common-garden experiments. D. galeata individuals from different time periods and latitudes were submitted to various water temperatures in flow-through-systems. In all experiments elevated water temperatures were shown to result in an increased somatic growth rate and accordingly an earlier age at maturity. In addition to the observed phenotypic plasticity, significant temperature x age interactions and temperature x origin interactions indicate thermal micro-evolution within last decades. With regard to these patterns of adaptation, we discuss the consequences of global warming on the fate of Daphnia populations and European freshwater biotas.