Density-dependent evolution of life-history traits in Drosophila melanogaster

Abstract

Populations of Drosophila melanogaster were maintained for 36 generations in r- and K-selected environments. In the r-selection environment, populations were reduced to low densities by density-independent adult mortality, whereas populations in the K-selection environment were maintained at their carrying capacity. Relative to the r-selected populations evolved an increased larval-to-adult viability, larger body size, and longer development time at high larval densities. K-selected populations also have a higher rate of population growth at high densities. Other predictions of the theory are contradicted by the lack of differences between populations in adult longevity and fecundity and a slower rate of development for r-selected individuals at low densities. Differences between selected populations in larval survivorship, larval-to-adult development time, and adult body size are strongly dependent on larval density, and there is a significant interaction between populations and larval density for each trait. This manifests an inadequacy of the theory on r- and K-selection, which does not take into account such interactions between genotypes and environments. -from Authors