Does environmental variability limit niche overlap?

A stochastic theory of limiting similarity is presented that attempts to quantify the relationship between tolerable niche overlap among competing species and the degree of environmental fluctuation. The theory is based on a heuristic analytical approximation that provides conditions under which a rare invading species can increase in the presence of a community of established competitors. The major qualitative conclusion, derived from investigating two symmetric, discrete-time, stochastic analogs of the Lotka-Volterra competition equations, is that weak to moderate stochastic variation does not appear to limit significantly the similarity of competing species. This result is in sharp contrast to the conclusions of May and MacArthur's pioneering study of stochastic limiting similarity. A possible reason for this discrepancy is explored.