Interactive Factors: Competition, Mixed-Species Benefits and Coevolution

Abstract

To understand the many studies of competition and niche segregation (or “resource partitioning”) among fishes, it is necessary to place them in the context of historical thinking in ecology about “the niche,” competition, and community structure. Stimulated by the empirical or conceptual work of Grinnel (1917), Elton (1927), Hutchinson (1957a), MacArthur (1958), and others, generations of ecologists studied community structure from the perspective that animals have “niches,” that typical communities are relatively stable equilibrium (or at least predictable) entities, and that over the course of evolutionary or ecological time, coevolution results in the members of a community segregating along important resource axes, permitting similar (but not ecologically identical) species to coexist. Competition between species was generally accepted as a (if not “the”) driving force in the structure of communities.

What groups crowd upon each other in the struggle for subsistence? Do closely allied species (of fishes), living side by side, ever compete for food? What relation, if any, do specific and generic differences bear to differences of food? ... Prominent peculiarities ... will probably be found merely to extend a little the capacities of the species, or to enable it to take those slight advantages of its competitors when the struggle for existence comes to the death grapple.... That a full understanding of the competitions among the fishes of a stream or lake is necessary... is evident at once.

Forbes (1878)

... so the existence of an animal may be decided by the presence or absence of some structural modification adapted to carry it safely through a single brief period of unusual scarcity or of extraordinary competition.

—Forbes (1888b)