Genetic variation and the ecological parameter "food medium" in cage populations of Drosophila melanogaster.

Impressive effects of the ecological factor "food medium" upon the frequencies of the lethal-bearing second chromosomes in Drosophila melanogaster were found in cage populations originated from a common gene pool. Allozyme frequencies for two second enzyme loci were also determined. The lethal frequencies found were higher when the environmental was restrictive than when it was favorable. Moreover, the lethal frequencies were higher in populations of smaller size than in those of greater. The role of the lethal genetic variants in the structure of populations is discussed.