Rapid evolution of thermal tolerance in the water flea Daphnia

Global climate is changing rapidly, and the degree to which natural populations respond genetically to these changes is key to predicting ecological responses. So far, no study has 25 documented evolutionary changes in the thermal tolerance of natural populations as a response to recent temperature increase. Here, we demonstrate genetic change in the capacity to tolerate higher temperatures in the water flea Daphnia using both a selection experiment and the reconstruction of evolution over a period of forty years using a layered dormant egg bank. We observed a genetic increase in thermal tolerance in response to a two-year ambient + 4 °C selection treatment and in the genotypes of natural populations from the 1960s and 2000s hatched from lake sediments. This demonstrates that natural populations have evolved increased tolerance to higher temperatures, likely associated with increased frequency of heat waves over the past decades, and possess the capacity to evolve increased tolerance to future warming.

Publication year:2015