Evolutionary responses of the life history of wild-caught Drosophila melanogaster to two standard methods of laboratory culture

Genetic adaptation of wild populations to captivity can be a problem for st udies of evolution and for programs of conservation and biological control. We examine how the life history of Drosophila melanogaster, the most commo nly used organism for laboratory studies of evolution, evolves in response to two common methods of laboratory culture: in bottles and in population c ages. We collected flies at the same site in nature at the same time of yea r in three consecutive years and compared freshly collected populations fro m the third collection with the products of 1 or 2 yr's laboratory culture, in a replicated experimental design. Preadult development time increased i n the laboratory, particularly in cage culture. There was also an increase in larval competitive ability in both types of culture. Body size was littl e affected, increasing slightly and only in the bottle culture. Early fecun dity increased in bottle culture, while late fecundity declined. Adult mort ality rates were lowest in the fresh collections and showed a marked and pr ogressive increase in bottle culture with a slight increase in population c age culture and apparently only in the first year of culture. Remating freq uency increased in bottle but not cage culture. These evolutionary changes are most likely explained by increased larval competition in laboratory cul ture, especially in population cages, and by truncation of the adult period in the bottle culture, resulting in natural selection acting solely on the early part of the adult period.