On environmental variability and limits to similarity

Different model approaches to the problem of environmental variability and limits to similarity are reviewed. It is shown that the assumption of a strictly flat resource spectrum leads to singular results. Hence, the result of May & MacArthur that a qualitative difference exists between a constant and a weakly varying environment is not generally valid. For small variations in the environment, several of the models reduce to a common form and the limits to similarity depend only weakly upon the magnitude of the environmental fluctuations.