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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 811

Martin E. Boraas, Dianne B. Seale, and J. Brian Horton; Resource competition between two rotifer species (Brachionus rubens and B. calyciflorus): an experimental test of a mechanistic model. J.Plankton Research 12(1):77-87, 1990

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A mechanistic model of competition on a single resource was tested experimentally with two freshwater rotifers, Brachionus rubens and Brachionus calyciflorus, both grown on the alga Chlorella pyrenoidosa. Using open culture systems for each species we measured: (i) the resource-saturated exponential growth rate, (Umax), and (ii) the relationship between specific growth rate, (U), at steady-state and the residual algal concentration over a range of system turnover rates, or dilution rates, (D). The (Umax) 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 models, B. calyciflorus was the dominant species at rapid (D) (0.029 hr-1) and B. rubens was dominant at slow (D) (0.0044 hr-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.