The micro-evolutionary potential of Daphnia magna population exposed to temperature and cadmium stress

This study examines micro-evolutionary aspects of a natural Daphnia magna population exposed to Cd. To this end, a set of hypotheses related to micro-evolutionary responses and to how these are influenced by temperature and Cd stress, were tested. Life-table experiments were conducted with 14 D. magna clones collected from an unpolluted lake following a 2×2 design with Cd concentration and temperature as the factors (control vs. 5 μg/L cadmium, 20 vs. 24 °C). Several fitness traits were monitored during 21 days. Our results demonstrate (1) that chemicals can have effects on key population genetic characteristics such as genetic variation and between-trait correlations and (2) that these effects may differ depending on temperature. Their findings also suggests that further research is needed to understand the importance of combined chemical–global warming stress for micro-evolutionary responses of organisms. These aspects are currently not accounted for in any regulatory environmental risk assessment procedure.