The senescence of Daphnia from risky and safe habitats

Evaluating life history in an ecological context is critical for understanding the diversity of life histories found in nature. Lifespan and senescence differ greatly among taxa, but their ecological context is not well known. Life history theory proposes that senescence is ultimately caused by a reduction of the effectiveness of natural selection as organisms age. A key prediction is that different levels of extrinsic mortality risk lead to the evolution of different senescence patterns. I quantified both mortality risk and investment in late‐life fitness of Daphnia pulex‐pulicaria , a common freshwater zooplankter. I found that Daphnia from high‐risk pond habitats invest relatively little in late‐life fitness, whereas those from low‐risk lake habitats invest relatively more in late‐life fitness. This suggests that ecological approaches can be useful for understanding senescence variation.