Analysis of microdifferentiation in a Spanish cellar population of Drosophila melanogaster.

Variation in Adh and alpha Gpdh-1 gene frequencies has been used to check for microdifferentiation in Spanish samples of Drosophila melanogaster inside and outside a wine cellar. Flies were collected after vintage and after overwintering respectively; within each period samples were taken on up to five consecutive days each month. Variation of gene frequencies of Adh and alpha Gpdh-1 can be considered random when samples collected each month are taken into account. When mean monthly frequencies are considered, alpha Gpdh-1 does not show any significant variation all over the year; yet, variation of the frequency of AdhS shows a cyclical pattern, its frequency being maximum at the end of the summer and minimum after overwintering. Due to the parallel change of the frequency of the inversion In(2L)t and the AdhS allele, no decision can be made whether the Adh locus itself or the inversion are responsible for the changes.