Does variation in the intensity and duration of predation drive evolutionary changes in senescence?

1. The evolutionary theory of senescence predicts that increased rates of extrinsic mortality select for faster declines in fertility and survival with age. One predicted mechanism is that increased mortality favors alleles that enhance fitness early in life at the expense of survival or reproduction later in life (antagonistic pleiotropy). 2. We tested these predictions in natural populations of Daphnia ambigua from lakes that vary in the severity and duration of fish predation. Daphnia are found in lakes with: (1) anadromous alewife (Alosa pseudoharengus) that migrate between marine and freshwater, (2) permanent landlocked alewife, and (3) no alewife. Daphnia are rare year-round in ‘landlocked lakes’ and are seasonally eliminated from the water column in ‘anadromous lakes’ due to the very strong predatory impact of anadromous alewife on populations of zooplankton. Previous work has also shown that intense seasonal bouts of predation by anadromous alewife has selected for increased all...