Resource overlap between co-occurring copepods: effects of predation and environmental fluctuation

Abstract

Two high-altitude copepods, Diaptomus shoshone and D. coloradensis, exhibit temporal differences in development and abundance, and they are of different size. Studies of adult sizes attained and of diets reveal that competition for resources between the two species is slight; however, laboratory experiments demonstrate that D. shoshone, the larger of the two species, preys extensively upon D. coloradensis. The population characteristics of the two species can be attributed both to avoidance of predation by the smaller species and to high variation in season length. Results are discussed in relation to theory, indicating that competition is a primary determinant of degree of resource overlap between congeneric species.