Ecology 5th Edition by Manuel Molles

Exercise 2

We included spatial refuges, predator satiation, and size in our discussions of the role played by refuges in the persistence of exploited species. How could time act as a refuge? Explain how natural selection could lead to the evolution of temporal "refuges."
Joseph Culp and Gary Scrimgeour (1993) studied the timing of feeding by mayfly larvae in streams with and without fish. These mayflies feed by grazing on the exposed surfaces of stones, where they are vulnerable to predation by fish, which in the streams studied are size-selective feeders and feed predominantly during the day. In the study streams without fish, both small and large mayflies have a slight tendency to feed during the day but feed at all hours of the day and night. In the streams with abundant fish populations, small mayflies fed around the clock, while large mayflies fed mainly at night. Explain these patterns in terms of time as a refuge and size-selective predation.