Evolutionary mechanisms underpinning fitness response to multiple stressors in Daphnia

Multiple stressors linked to anthropogenic activities can influence how organisms adapt and evolve. So far, a consensus on how multiple stressors drive adaptive trajectories in natural populations has not been reached. Some meta-analysis reports show predominance of additive effects of stressors on ecological endpoints (e.g. fecundity, mortality), whereas others show synergistic effects more frequently. Moreover, it is unclear what mechanisms of adaptation underpin responses to complex environments.

Here, we use populations of the crustacean Daphnia magna resurrected from different times in the past to investigate mechanisms of adaptation to multiple stressors, and to understand how historical exposure to environmental stress shapes adaptive responses of modern populations. Using common garden experiments on resurrected modern and historical populations, we investigate: i) whether exposure to one stress results in higher tolerance to a second stressor; ii) the mechanisms of adaptatio...