Structure and Stability in Natural and Randomly Constructed Competitive Communities

Abstract

Lyapunov stability and community structure in mathematical models of competitive communities are examined with "neutral models." The calculated stability, average alpha, and alpha variance of observed communities are compared with those of analogous randomly constructed communities. Calculated stability decreases as the number of species increases in observed communities. However, observed communities are generally more stable than randomly constructed communities with the same number of species. This greater stability of observed communities is partly due to the low values of both the mean and variance of their alpha distributions. Randomization of consumer resource utilization rates almost always increased the mean but not the variance of the calculated consumer similarities. In comparison to randomly constructed communities, the lower similarities and greater stability of the observed communities suggest that competitive processes are important in shaping real communities.