Competitive interactions in Drosophila melanogaster IV. Chromosome assay

Abstract

The technique of chromosome assay, using chromosome substitution lines, has been refined in Drosophila melanogaster to provide a powerful method of investigating the distribution, amongst the chromosomes, of the underlying genetical determinants, particularly in relation to chaeta characters. In the present study this technique is extended to investigate differences in competitive ability. The genotypes used were two inbred lines chosen as showing differences in competitive ability based on a survey of such lines derived from a large laboratory population. The character followed was pa, the proportion (transformed into angles) of eggs which successfully developed into adults. It was found that chromosome III carried gene differences affecting both aggression and response but showing no good evidence of interaction with one another or with genes on other chromosomes. The gene differences on chromosome I, on the other hand, showed no main effect on either aggression or response but a clear interaction with chromosome II in affecting response. Chromosome II also showed a main effect on aggression, though only when associated with one of the two genetically marked lines with which the substitution lines were compared. The implications of these findings are discussed.