InterJournal Complex Systems, 916
Status: Accepted
Manuscript Number: [916]
Submission Date: 2004
Selection in Ecosystems
Author(s): Josh Mitteldorf ,John W. Pepper

Subject(s): CX.35



The notion that natural selection acts above all on individual reproductive capacity has been a mainstay of evolutionary theory since the origins of population genetics nearly a century ago. However, this assumption has rarely been subject to field tests, and in those few instances where direct, quantitative tests have been undertaken, the results suggests that nature does not always maximize individual reproductive capacity. Four broad phenomena of the biosphere have persisted in inspiring controversy because they seem to require higher levels of selection than can be justified by traditional models. These are: the ubiquity of sexual reproductive, despite a twofold disadvantage (by some counts) in r. The persistence of high levels of genetic diversity in wild populations mocks the theoretical fiat that all such diversity much be selectively neutral. Senescence is maintained as a near universal characteristic of the eukaryotic genome, despite its negative contribution to individual fitness. Evidence of reproductive restraint and "prudent predation" is widely accepted by field ecologists, but mocked as nonsense by evolutionary theorists. We propose that evolutionary dynamics of ecosystems can resolve these dilemmas. We present a simple model of ecosystem evolution that shows promise at resolving each of these paradoxes. The model tracks individuals of 4 species in a toy ecosystem, co-evolving on a viscous grid. In preliminary model results, we find that (1) sexual reproduction is maintained, (2) diversity does not collapse, (3) senescence is selected as an adaptation, and (4) neither predation nor reproductive potential are maximized. A key to understanding the model's behavior is the local interdependence of species, which supports the efficient punishment of any population that expands at the expense of the ecosystem.

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