From Populations to Ecosystems: Theoretical Foundations for a New Ecological Synthesis

Ecosystem ecology and evolutionary biology are two disciplines that have not had a history of close, peaceful relationships. They have been largely separate intellectual endeavors (Holt 1995), and when they have interacted, it has been more often to clash than to blend. The modern theory of evolution sees evolution as the result of a two-step process: trait variation is first generated at random by mutations or recombination of the genetic material, and natural selection then acts on this variation to sift out those traits that confer better adaptation to the environment. Since genes are carried, expressed, and transmitted by individual organisms, the individual organism is widely regarded as the main unit of selection, while the ecosystem in which the individual organism lives is viewed as part of the broad environmental context that determines the direction and strength of natural selection.

On the other hand, ecology is concerned with the multiple interactions that organisms have with their biotic and abiotic environment. As a discipline that studies the overall functioning of the systems made up of organisms and their environment, ecosystem ecology has had the natural tendency to view ecosystems as integrated units on their own and hence to search for laws and principles that govern the development and evolution of these higher-level units. Lotka (1922) had already proposed that, as a principle, “natural selection tends to make the energy flux through the system a maximum.” His argument was simple but cogent: “If sources are presented, capable of supplying available energy in excess of that actually being tapped by the entire system of living organisms, then an opportunity is furnished for suitably constituted organisms to enlarge the total energy flux through the system.” This idea was taken up by Odum in the form of his “maximum power principle” (H. T. Odum and Pinkerton 1955; H. T. Odum 1983), and by many others since in various guises. Other scientists have claimed that ecosystems evolve toward maximum entropy production, in agreement with the second law of thermodynamics (Schneider and Kay 1994). Yet others

-225-