Abstract
Considered is a rank-size relation reduced by a multi-species system. Each species in the community is characterized by the population size in an isolated region. It is easily able to be assigned the rank K(=1, 2, ...) of species from the largest to the smallest with respect to the population size. We discuss a rank-size relation of a stationary community, making use of a stationary solution for a multi-species system of diffusion equation with an exclusive interference among species.
