Patterns of selection: stress resistance and energy storage in density-dependent populations of Drosophila melanogaster.

Populations of Drosophila melanogaster subjected to extreme larval (CU) or adult (UC) densities for multiple generations were assayed for a variety of life history characters. When reared under either crowded or uncrowded larval conditions, populations which had been selected to tolerate the limitation of resources imposed by extreme larval (CU) crowding, exhibited greater starvation resistance and lipid content than did populations which do not routinely undergo larval density-dependent regulation. Previous studies have shown that the CU populations do not show a correlated increase in longevity; as has been generally observed for these characteristics in age-structured populations of D. melanogaster. This suggests that density-dependent natural selection may not always shape life histories of the same characteristic in the same direction that age-specific selection does.