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Evolution in species may reverse predator-prey population cycles

Georgia Institute of Technology

Populations of predators and their prey usually follow predictable cycles. When the number of prey increases - perhaps as their food supply becomes more abundant - predator populations also grow.



Researchers at the Georgia Institute of Technology have proposed a theory to explain these co-evolutionary changes. And then, using data collected by other scientists on three predator-prey pairs - mink-muskrat, gyrfalcon-rock ptarmigan and phage-Vibrio cholerae - they show how their theory could explain unexpected population cycles.


"Our work shows that co-evolution can yield new and unique behavior at the population scale," explained Joshua Weitz, an associate professor in the School of Biology at Georgia Tech. "When you include evolution, the classic prey-predator dynamics have a much greater range of possible outcomes. We are not replacing the original theory, but proposing a more general model that opens the door to these new phenomena."



"With predator and prey co-evolution, you can see oscillations in which there are lots of prey around even when there are many predators, or lots of predators around even when there are very few prey," noted Michael Cortez, a postdoctoral fellow in the Weitz lab and first author of the paper.

"When prey is abundant and there are few predators, it may be because there are lots of defended prey - prey that the predators can't eat," he added. "When there are lots of predators around and few prey, it's because the prey are very good food sources and the predators are doing quite well."




"This study identifies how adaptation between two species and interactions between their numbers can result in something different from what you would get if you just had the interaction between the numbers," said Cortez. "This is something that will show up across many ecological systems. We can now explain broad trends that occur in vastly different systems using a theoretical approach, and the fact that we can identify the mechanism responsible for it is unique to our study."


This research was supported by the National Science Foundation under Award DMS-1204401, and by the Burroughs Wellcome Fund. Any conclusions or opinions expressed are those of the authors and do not necessarily represent the official views of the sponsoring agencies.

CITATION: Michael H. Cortez and Joshua S. Weitz, "Coevolution Can Reverse Predator-Prey Cycles," (Proceedings of the National Academy of Sciences, 2014).
