Unveiling the complete invasion history of D. melanogaster : three horizontal transfers of transposable elements in the last 30 years

Transposable elements (TEs) are repetitive sequences capable of mobilizing within genomes, exerting significant influence on evolution throughout the tree of life. Using a novel approach that does not require prior knowledge about the sequence of repeats, we identified three novel TE invasions in D. melanogaster : MLE spread between 1990-2000, Souslik between 2009-2012, and Transib1 between 2013-2016. We recapitulate prior findings, revealing that a total of 11 TEs invaded D. melanogaster over the past two centuries. Leveraging data from over 1400 arthropod genomes, we provide evidence that the TE invasions were triggered by horizontal transfers, with D. simulans and species of the D. willistoni group acting as putative donors. Through analysis of ∼ 600 short-read datasets spanning diverse geographic regions, we reveal the rapidity of TE invasions: Transib1 swiftly multiplied from three isolated epicenters in 2014 to all investigated populations within just two years. Our findings suggest that anthropogenic activities, facilitating habitat and population expansions of D. melanogaster , might have accelerated the rate of horizontal transposon transfer as well the spread of the TEs into the worldwide population. Given the significant impact of TEs in genomes and the potential involvement of humans in their dispersal, our research has crucial implications for both evolution and ecology.