The P-element strikes again: the recent invasion of naturalDrosophila simulanspopulations

The P-element is one of the best understood eukaryotic transposable elements. It invaded Drosophila melanogaster populations within a few decades, but was thought to be absent from close relatives, including D. simulans . Five decades after the spread in D. melanogaster , we provide evidence that the P-element has also invaded D. simulans . P-elements in D. simulans appears to have been acquired recently from D. melanogaster probably via a single horizontal transfer event. Expression data indicate that the P-element is processed in the germline of D. simulans , and genomic data show an enrichment of P-element insertions in putative origins of replication, similar to that seen in D. melanogaster . This ongoing spread of the P-element in natural populations provides an unique opportunity to understand the dynamics of transposable element spreads and the associated piRNA defense mechanisms.