Niche breadth in Bryozoa as a test of competition theory

Abstract

COMPETITION theory predicts that intraspecific and interspecific competition should often have opposite effects on the use of resources by a population, the former increasing, the latter decreasing, the range of resource actually used^1,2. Field data supporting these predictions are well known for the interspecific case^3,4 but are scarce for the intraspecific condition, and we have been unable to find any reference demonstrating both effects within a single species. We therefore report here the verification of both predictions in respect of competition for space by the epiphytic bryozoan Alcyonidium hirsutum; less extensive data suggesting the same effects within other bryozoans are also reported.