Adaptation of Drosophila melanogaster to increased NaCl concentration due to dominant beneficial mutations.

New beneficial mutations, combined with selection, were responsible for quick adaptation of Drosophila melanogaster to a novel environment. Using a highly inbred homozygous stock of D. melanogaster, we observed that in thirty generations the original stock had evolved to resist a previously toxic level of dietary salt (NaCl) and to produce a significantly higher number of progeny when reared in elevated salt concentrations. Survival in higher salt-stressed environments was due to new dominant genetic changes on the second and third chromosomes.