Paper Reviewed
Geerts, A.N., Vanoverbeke, J., Vanschoenwinkel, B., Van Doorslaer, W., Feuchtmayr, H., Atkinson, D., Moss, B., Davidson, T.A., Sayer, C.D. and De Meester, L. 2015. Rapid evolution of thermal tolerance in the water flea Daphnia. Nature Climate Change 5: 665-668.

In a paper published in Nature Climate Change, Geerts et al. (2015) describe how they were able to "demonstrate genetic change in the capacity of the water flea Daphnia to tolerate higher temperatures using both [1] a selection experiment and [2] the reconstruction of evolution over a period of forty years derived from a layered dormant egg bank."

In the first case, the ten researchers discovered that clones from the heated mesocosms they created had, on average, a 3.6°C higher CTMax (critical thermal maximum) than clones from the ambient-temperature mesocosms they maintained, while also noting that "the difference in CTMax between the populations from the two temperature treatments matched the +4°C temperature difference between the two selection regimes."

In light of this pair of separate findings, the ten scientists logically concluded that their results clearly demonstrate that (1) "natural populations have evolved increased tolerance to higher temperatures, probably associated with the increased frequency of heat waves over the past decades," and that (2) they therefore also likely "possess the capacity to evolve increased tolerance to future warming." In fact, they state that their study "is the first to demonstrate both the capacity for rapid evolution of thermal tolerance and actual genetic change over recent decades associated with climate change in natural populations," adding that their study "is the first to demonstrate both [1] the capacity for rapid evolution of thermal tolerance and [2] actual genetic change over recent decades associated with climate change in natural populations."