The limits of stress-tolerance for diapausing resting stages in freshwater ponds

Abstract

Abstract In seasonal environments, many organisms evolve strategies such as diapause to survive stressful periods. Understanding the link between habitat stability and diapause strategy can help predict population’s survival in a changing world. Freshwater organisms may survive periods of drought or freezing only with the help of durable resting stages. The frequency and extent of drought or freezing vary strongly among habitats and are predicted to change as a consequence of climate change raising questions about an organism’s ability to cope with different forms of stress. Using Daphnia magna as a model system, we tested resting stages from different populations for their ability to cope with stress during diapause. The combination of elevated temperatures and wet conditions during diapause shows to prevent hatching altogether. In contrast, hatching is relatively good after a dry and warm diapause, but declines with rising temperatures, while time to hatching increases. Resting stages produced by populations from summer-dry habitats perform slightly, but consistently, better at higher temperatures and dryness, supporting the local adaptation hypothesis. Considering that temperatures and summer droughts are projected to increase in upcoming years, it is fundamental to know how resting stages resist stressful conditions so as to predict and protect the ecological functioning of freshwater ecosystems.