Most theoretical and experimental work on stoichiometry and population interactions deals with situations where growth of the focal populations depends on two nutrient resources, or one nutrient resource and another factor such as a predator. Some progress has been made in understanding situations where two populations compete for two nutrients, and a predator attacks both of them while recycling a proportion of one or both nutrients. Such a scenario is common for planktonic algae, where zooplankton herbivores recycle dissolved nitrogen and phosphorus required by the algae. Without the predator, stable coexistence of two competitors on two resources is likely, in a range of nutrient supplies that make this feasible (e.g., Figure 2). In some theoretical scenarios, the predator merely shifts the range of nutrient supplies where such stable coexistence is feasible. In other cases, the predator destabilizes coexistence, so that priority effects occur. Another theoretical possibility is destabilization resulting in persistent periodic or chaotic dynamics.
When the number of nutrient resources increases to three, dynamical complexity is a possibility even in the absence of predators. If the stoichiometry of consumption for the three nutrients follows the right relationships among competing population, periodic dynamics or chaotic dynamics can arise with more than three populations persisting.
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