ADAPTATION TO COMPETITION BY NEW MUTATION IN CLONES OF ALEXANDRIUM MINUTUM.

We describe two competition experiments between clones of the dinoflagellate Alexandrium minutum. In the first experiment, two clones originating from a single haploid cell competed until one of the clones was almost driven to extinction. In the second experiment, these two clones were allowed to compete with the original populations, which were previously kept as cysts. The results indicate that an improvement of the competitive ability in both clones has occurred during the history of competition. This adaptation to competition must be attributed to selection acting on the new genetic variation that has arisen by mutation.