The Paradox of the Plankton Reconsidered; Or, Why Do Species Coexist?

Abstract

The coexistence of a large number of planktonic algae in turbulent water was termed by Hutchinson as a paradox because it contradicted the dominant notion of the competitive exclusion principle. Later the term paradox of the plankton was used also for coexistence in zooplankton. The modern analysis of the problem taking into account the progress achieved during the 2 decades after publication of Hutchinson''s paper shows that the paradox of the plankton does not become less paradoxical, if one explains it from the traditional point of view appealing to the niche divergence or environmental instability. Another approach is possible which admits the coexistence principle as an empirical generalization and admits the possibility of a parallel evolution of closely allied species limited by the same set of resources. Since the paradox is a statement contradicting the theory, the question whether the paradox of the plankton really exists may be replaced by the question: what is the theory in ecology; only mental constructions such as competitive exclusion principle or also generalizations of empirical data?