RESOURCE COMPETITION BETWEEN 2 ROTIFER SPECIES (BRACHIONUS-RUBENS AND B-CALYCIFLORUS) - AN EXPERIMENTAL TEST OF A MECHANISTIC MODEL

A mechanistic model of competition on a single resource was tested experimentally with two freshwater rotifers, Brachionus rubens and B.calyciflorus, both grown on the alga Chlorella pyrenoidosa. Using open culture systems for each species we measured: (i) the resource-saturated exponential growth rate, μmax, and (ii) the relationship between specific growth rate, μ, at steady-state and the residual algal concentration over a range of system turnover rates, or dilution rates, D. The μmax of B.calyciflorus was ̃60% higher than B. rubens. These results were then used to construct a graphical model for predicting the victor in interspecific competition between the two rotifers. Since the two resource-dependent growth rates crossed, one species, B.calyciflorus, was predicted to be the victor at a high D while B. rubens was predicted as the victor at low D. Finally, the outcome of competition was determined for two turnover rates. As predicted by the graphical competition models, B.calyciflorus was the dominant species at rapid D (0.029 h-1) and B.rubens was dominant at slow D (0.0044 h-1). These studies support recent conclusions that mechanistic competition models may be applied to predict dominant species from a priori information on growth potential and resource levels, which is not possible with traditional Lotka-Volterra models. © 1990 Oxford University Press.