The Drosophila melanogaster P transposable element provides one of the best cases of horizontal transfer of a mobile DNA sequence in eukaryotes. Invasion of natural populations by the P element has led to a syndrome of phenotypes known as “P-M hybrid dysgenesis” that emerges when strains differing in their P element composition mate and produce offspring. Despite extensive research on many aspects of P element biology, questions remain about the stability and genomic basis of variation in P-M dysgenesis phenotypes. Here we report the P-M status for a number of populations sampled recently from Ukraine that appear to be undergoing a shift in their P element composition. Gondal dysgenesis assays reveal that Ukrainian populations of D. melanogaster are currently dominated by the P’ cytotype, a cytotype that was previously thought to be rare in nature, suggesting that a new active form of the P element has recently spread in this region. We also compared gondal dysgenesis phenotypes and genomic P element predictions for isofemale strains obtained from three worldwide populations of D. melanogaster in order to guide further work on the molecular basis of differences in cytotype status across populations. We find that the number of euchromatic P elements per strain can vary significantly across populations but that total P element numbers are not strongly correlated with the degree of gondal dysgenesis. Our work shows that rapid changes in cytotype status can occur in natural populations of D. melanogaster, and informs future efforts to decode the genomic basis of geographic and temporal differences in P element induced phenotypes

Phenotypic and genomic analysis of P elements in natural populations of Drosophila melanogaster