Hybrid dysgenesis is defined as a syndrome of aberrant genetic traits that are induced progeny of certain crosses between strains of Drosophila melanogaster . The main objective of this work was to classify the freshly collected strains as to the potential of P element activity and their regulatory ability to elements from Harwich control strains. Our results for natural populations collected in Rio Grande do Sul, Brazil, and Colombia, show that these are type Q, since all tested strains carry the P element , by molecular criteria, and presented a low P activity . Likewise, these strains are not very susceptible to the action of the elementP . Greater values of susceptibility and activity were found in the Colombian population, agreeing with the hypothesis of the clinal distribution of the activity of this element.
