Inferring interspecific competition from patterns of species abundance: a study of phytoplankton and nocturnal flying insect assemblages.

Abstract

Based on our hypothesis that the phytoplankton assemblage of South Fishtail Bay in Douglas Lake would have a significantly higher degree of interspecific competition than the nocturnal flying insect assemblage attracted to a black light at UMBS, we examined the two assemblages to compare and contrast the relative abundances for each. Biomass/biovolume was determined to be a more accurate index of resource capture and therefore competitive success than was number of individuals. In the phytoplankton and macroinsect assemblages, we found a few very common species and many rare ones; in the microinsects the relative abundance was more random. Patterns of relative abundance as expressed in rank abundance diagrams were found to have significant, though limited, usefulness as indicators of degree of interspecific competition within a species assemblage.