The recent invasion of natural Drosophila simulans populations by the P-element

Significance Transposable elements (TEs) persist via two evolutionary strategies—in the short term, they selfishly propagate within genomes, and over the long term, they spread horizontally between species. Famously, the P-element invaded Drosophila melanogaster populations some time before 1950 and spread rapidly worldwide. Here, we show that it has also invaded a close relative, Drosophila simulans , from which it was absent until recently. The genomic tools at our disposal offer the unique opportunity to study the dynamics of a TE invasion at multiple levels and to compare the spread of the P-element in D. simulans with the well-investigated invasion of D. melanogaster .