Spatiotemporal Tracking of Three Novel Transposable Element Invasions in <i>Drosophila melanogaster</i> over the Last 30 Years

Transposable elements (TEs) are repetitive sequences capable of mobilizing within genomes, exerting a significant influence on evolution throughout the tree of life. Using a novel approach that does not require prior knowledge of the sequence of repeats, we identified three novel TE invasions in Drosophila melanogaster: McLE spread between 1990-2000, Souslik between 2009-2012, and Transib1 between 2013-2016. We recapitulate previous findings, revealing that a total of 11 TEs invaded D. melanogaster over the past two centuries. These 11 invasions increased the fly genome by ∼1 Mbp. Using data from over 1,400 arthropod genomes, we provide evidence that these TE invasions were triggered by horizontal transfers, with Drosophila simulans and species of the Drosophila willistoni group acting as putative donors. Through the 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 in just 2 years. Our findings suggest that anthropogenic activities, which facilitate the range and population expansions of D. melanogaster, could have accelerated the rate of horizontal transposon transfer as well as the spread of the TEs into the worldwide population. Given the significant impact of TEs on evolution and the potential involvement of humans in their dispersal, our research has crucial implications for both evolution and ecology.