| My research has produced evidence in support of the hypothesis that selection can occur at the community or ecosystem level. I review the original literature with regard to the debate between the "organismal" and "individualistic" perspectives on the organization of ecological communities, discussing an alternative interpretation based on multilevel selection theory and complex systems studies. I report the results of three sets of experiments that test the hypothesis that selection can operate at the community or ecosystem level of biological organization. The first set of experiments involved two components: (1) artificial selection of Arabidopsis thaliana rhizosphere ecosystems for their effect on plant growth, and (2) artificial selection of aquatic microbial communities to alter the pH of the medium. The second set of experiments involved selection of aquatic microbial communities for their ability to break-down the xenobiotic, 3-choloraniline, demonstrating a potential application of artificial ecosystem selection. The third set of experiments returned to the rhizosphere ecosystem, but the competitive relationship between two species of plants was the ecosystem phenotype subjected to selection. Results of the first two sets of experiments support the ecosystem-level selection hypothesis. To conclude, I review literature describing the biological complexity of rhizosphere ecosystems and suggest a research program to investigate rhizosphere ecology from a multilevel-selection/complex systems perspective. |
