Colonization Curves: Application to Stream Insects on Semi-Natural Substrates

Abstract

Aquatic insects were allowed to colonize gravel filled trays placed in a small stream. The rate of accumulation of individuals on the trays can be described by a power function Nt = atb or an equilibrium model of form Nt = k/m (1-e-mt). Both models fit the data but the empirical power function is more convenient. [Nt = number present at time t, k/m = asymptotic number of individuals present after infinite and e = base of natural logarithms.] Colonization rates vary between taxa and depend significantly on location in the study section. The parameters of fitted curves permit objective comparisons of colonization by different species and in different environments. The significant location effect suggests that the fauna of each portion of the stream bottom is influenced substantially by that of adjacent units.