Trade-off between <i>r</i> -selection and <i>K</i> -selection in <i>Drosophila</i> populations

Abstract

Density-dependent genetic evolution was tested in experimental populations of Drosophila melanogaster subject for eight generations to natural selection under high (K-selection) or low (r-selection) population density regimes. The test consisted of determining at high and at low densities the per capita rate of population growth of the selected populations. At high densities, the K-selected populations showed a higher per capita rate of population growth than did r-selected populations, but the reverse was true at low densities. These results corroborate the predictions derived from formal models of density-dependent selection. However, no evidence of a trade-off in per capita rate of growth was observed in 25 populations of D. melanogaster, each homozygous for a different second chromosome sampled from a natural population.