Genetic variability of quantitative traits in Drosophila melanogaster (fruit fly) natural populations: Analysis of wild-living flies and of several laboratory generations

Wild-collected Drosophila melanogaster females were isolated in culture vials to initiate isofemale lines in the laboratory. Wing length and body pigmentation (thorax, abdominal segments 5, 6 and 7 and their sum) were measured in wild flies and in successive laboratory generations. Heritability was estimated by parent-offspring regression between wild-living flies and laboratory progeny or by calculating intraclass correlation between lines in each laboratory generation. For wing length, phanotypic variability was much higher in nature than in the laboratory, and the estimated heritability with parent-offspring regression (0.14) was significant but quite low. Within laboratory generations, intraclass correlation was much higher, on average 0.34. For pigmentation characteristics, variability in nature was similar to that measured in the laboratory. Parent-offspring regressions produced significant and high heritability values (range 0.40-0.62), except for abdomen segment 5. Intraclass correlations were also significantly greater than zero for all traits (range 0.22-0.47), including segment 5. The stability of the lines over successive laboratory generations was shown by the stability of the overall mean and by a strong positive correlation between family means of successive generations. The correlation across generations demonstrates a genetic repeatability of the trait and should be useful in experiments using isofemale lines.