Rapid evolution of antioxidant defense in a natural population of Daphnia magna

Natural populations can cope with rapid changes in stressors by relying on sets of physiological defense mechanisms. Little is known onto what extent these physiological responses reflect plasticity and/or genetic adaptation, evolve in the same direction and result in an increased defense ability. Using resurrection ecology, we studied how a natural Daphnia magna population adjusted its antioxidant defense to ultraviolet radiation (UVR) during a period with increasing incident UVR reaching the water surface. We demonstrate rapid evolution of the induction patterns of key antioxidant enzymes under UVR exposure in the laboratory. Notably, evolutionary changes strongly differed among enzymes and mainly involved the evolution of UV-induced plasticity. While D. magna evolved a strong plastic upregulation of glutathione peroxidase under UVR, it evolved a lower plastic upregulation of glutathione S-transferase and superoxide dismutase, and a plastic downregulation of catalase. The differential...