No evidence for frequency-dependent selection acting between clones of the water flea, daphnia magna

Abstract

Competition experiments were carried out between clones of the water flea, Daphnia magna, in an effort to detect frequency-dependent selection maintaining clonal coexistence. Pairs of clones were used, both from the same and from different sources. No stable equilibrium was detected, but in the first series of experiments, in which gene frequencies were assessed by the electrophoresis of samples, it was found that differences in the level of sexuality between clones were resulting in artificial selection.A second series of experiments involved competition between morphologically distinguishable clones. An analysis of the computed selection acting on the populations, and reproductive rate differences, failed to show significant effects of clone frequency on these quantities in the experiments. There was some evidence that reproductive rate differences between clones were selectively important. © 1981 The Genetical Society of Great Britain.