Analysis of allozymic and quantitative variation produced by artificial selection in Drosophila melanogaster

In order to study a possible connection between allozymic and quantitative variation in D. melanogaster, three selection experiments were carried out, using founder strains of known genetic and chromosomal composition.The Adh and Gpdh-1 enzyme loci have been used as genetic markers and the maximum wing length has been the quantitative trait chosen. Two selected lines (high and low) were maintained and also one without selection (drift), to estimate the effect of random fluctuation on gene frequency variation. The allozymic variation was analysed by means of a polynomial regression, and a normal linear model allowed to make pairwise comparisons.The allelic combination ((F), A(-)) was favoured in the low lines of the selection experiments; the selection acted in favour of homozygotes, with a correlated loss of genetic homoeostasis. The similar behaviour of the drift and the control lines shows that random fluctuations in the gene frequencies in selected lines are negligible.