Viability in strains of Drosophila melanogaster submitted to artificial selection for wing shape divergence. Libéria Torquato, Blanche Bitner-Mathé. UFRJ, Rio de Janeiro, Brazil.

   Many studies suggest that artificial selection and inbreeding can lead to a decrease in viability. To obtain strains of D. melanogaster with divergent wing shape, we have performed a program of artificial selection with two biological replicates (named 1 and 5) at 22ºC. For each biological replicate, three strains were established: one with selection for elongated wings (L strain), one with selection for rounded wings (R strain), and a control strain with no selection applied (C strain). In this study, we investigated a possible effect of selection on the viability of each strain, in the 123th generation. Vials with 30 eggs from each strain were reared at 25ºC until adult emergence. The viability was calculated as the percentage of adults that actually emerged. And the effects of selection (L, R or C) and replicates (1 and 5) were tested using ANOVA. If selection has had a significant influence on viability in this selection program, we would expect to observe decreased viability in the selection strains (L and R) from both replicates, so that the interaction between selection and replicate would be non-significant. But this was not the case. We observed a highly significant interaction between these effects, as follows. Replicate 1 presented a significant lower viability in the selected strains (L and R strains) relative to the non-selected control strain (C strain). In contrast, no significant difference in viability was observed across L, R or C strains from replicate 5, this contrasting result indicates that selection might not be the factor affecting viability, which leaves genetic drift as an alternative hypothesis to explain the lower viability observed in replicate 1.