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ArticlesCopyright © 1991 by American Association for the Advancement of Science
Density-dependent natural selection and trade-offs in life history traits
Department of Ecology and Evolutionary Biology, University of California, Irvine 92717.
Theories of density-dependent natural selection state that at extreme population densities evolution produces alternative life histories due to trade-offs. The trade-offs are presumed to arise because those genotypes with highest fitness at high population densities will not also have high fitness at low density and vice-versa. These predictions were tested by taking samples from six populations of Drosophila melanogaster kept at low population densities (r-populations) for nearly 200 generations and placing them in crowded cultures (K-populations). After 25 generations in the crowded cultures, the derived K-populations showed growth rate and productivity that at high densities were elevated relative to the controls, but at low density were depressed.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)