Logistic interaction of natural populations of two species of waterboatmen

TitleLogistic interaction of natural populations of two species of waterboatmen
Publication TypeJournal Article
Year of Publication1977
AuthorsIstock CAlan
JournalThe American Naturalist

Commenting on Volterra's (1931) logistic theory of interspecific competition, MacArthur (1972) said that one of the main goals of such theory is to inspire experiments like those of Gause (1934). He went on to assert that the other main goal of theory is to inform us when we have a coherent explanation with all necessary ingredients. Volterra's theory did this too. It showed that simple equations might lead to coexistence or to one species replacing another, and it told us which to expect. In these respects, the Volterra theory...has been an unqualified success. However, it does have its limitations. It is probably never literally correct. Very likely no population ever grows exactly according to Volterra's equations. Ecologists who use them are following reasoning, something like this: The true, correct equations are probably "near to" the behavior of the solutions of Volterra equations. This paper presents a logistic analysis of field experiments designed to ask how "near to" or "literally correct" the Volterra theory might be for co-occurring populations of two waterboatment species (Corixidae). The experiments were suggested by Volterra's theory and Gause's experiments, but were designed to extend the empirical analysis to populations in nature. Surprisingly, the Volterra model comes out more "literally correct" than most ecologists would probably expect.