How many genes are selected in populations of Dacus oleae.

Three natural populations of Dacus oleae have been sampled for six electrophoretically detected polymorphic genes. The distribution of the allele frequencies in the different populations were analyzed by the method suggested by Lewontin and Krakauer (1973) (the various in space one) in order to test for selective neutrality. This method, however, which in our case showed that one or more genes are or have been subjected to selection, does not permit estimation of the number of selected loci. An improvement of this method is proposed that perimts a minimum estimation of the selected genes. About a third of them seem to be selected in our material. In our case however, where a cytological analysis is not possible, genes are not differentiated from possible inversions including these genes.