A contribution to the study of linkage disequilibrium in Drosophila melanogaster.

Linkage disequilibrium was detected in 12 out of 30 cases involivng gene alleles and inversions in three cage populations and in a natural population of Drosophila melanogaster from Greece. The cage populations possessed practically the same gene pool at their origin and were maintained simultaneously under the effects of the ecological factors "food medium" and "humidity". It is dicussed that the correlation of the same direction found between the frequencies of nonallelic elements of Adh locus and In (2L) 22D-34A or In (2R)52A-56F in such different populations as American, Japanese (Mukai et al;, 1971, 1974; Langley et al., 1974) and Greek, as well as cage populations under different environmental conditions, could be attributed to the effect of epistatic selection. Moreover, it seems that the In(2L)22D-34A has a tendency to interact genetically with the alpha-Gpdh locus, particularly when the populations are maintained under crowding conditions. However, further data are needed to assess whether other cases of the observed nonrandom associations can be better explained as transient associations generated by random drift, or as the result of epistatic selection.