Before revision: Contemporary niche theory is a powerful conceptual framework for understanding URLanisms interact with each other and with their shared environment. Herewe show that, for a wide range of modeling assumptions, niche theoryis equivalent to a Minimum Environmental Perturbation Principle (MEPP): ecosystems URLanize into a state that minimizes the collective impact URLanisms on their environment. Different choices of environmental dynamics naturally give rise to distinct dissimilarity measures for quantifying environmental impact. The MEPP allows for the analysis of ecosystems with large numbers of species and environmental factors and provides a new avenue for analyzing ecological invasions.
After revision: Fifty years ago, Robert MacArthur showed that stable equilibria optimize quadratic functions of the population sizes in several important ecological models. Here, we generalize this finding to a broader class of systems within the framework of contemporary niche theory, and precisely state the conditions under which an optimization principle (not necessarily quadratic) can be obtained.