Figure 13.11 The importance of energy reserves in causing population cycling. (a) Daphnia galeata water fleas can store high amounts of energy, which allows them to survive and reproduce even after reaching carrying capacity. When energy reserves run out, the population crashes to very low numbers and then rebounds and continues to oscillate. (b) Bosmina longirostris water fleas can only store a low amount of energy, so as the population nears carrying capacity, they experience reduced survival and reproduction. As a result, the population remains near its carrying capacity and oscillates much less.

Data from C. E. Goulden and L. L. Hornig, Population oscillations and energy reserves in planktonic cladocera and their consequences to competition, Proceedings of the National Academy of Sciences 77 (1980): 1716–1720.