Evolutionary Responses of the Life History of Wild‐Caught Drosophila melanogaster to Two Standard Methods of Laboratory Culture

Abstract

Genetic adaptation of wild populations to captivity can be a problem for studies of evolution and for programs of conservation and biological control. We examine how the life history of Drosophila melanogaster, the most commonly used organism for laboratory studies of evolution, evolves in response to two common methods of laboratory culture: in bottles and in population cages. We collected flies at the same site in nature at the same time of year in three consecutive years and compared freshly collected populations from the third collection with the products of 1 or 2 yr's laboratory culture, in a replicated experimental design. Preadult development time increased in the laboratory, particularly in cage culture. There was also an increase in larval competitive ability in both types of culture. Body size was little affected, increasing slightly and only in the bottle culture. Early fecundity increased in bottle culture, while late fecundity declined. Adult mortality rates were lowest in the fresh collections and showed a marked and progressive increase in bottle culture with a slight increase in population cage culture and apparently only in the first year of culture. Remating frequency increased in bottle but not cage culture. These evolutionary changes are most likely explained by increased larval competition in laboratory culture, 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.