Recent horizontal transfer of transposable elements in Drosophila

Abstract

Transposable elements are small pieces of DNA which selfishly increase in copy number within genomes. Transposable elements can also move between species through unknown intermediaries in a process known as horizontal transfer, infecting novel genomes and increasing in copy number. In this manuscript we used almost 400 dipteran genomes to uncover 648 recent transposon invasions, mostly in Drosophila. We limited our results to transposons with 99% similarity to capture recent transfers. When our results overlapped with previous studies they were largely replicated. The majority of transfers occurred between closely related species, with the cosmopolitan melanogaster group showing the highest recent transfer activity. However, we documented 60 HT events spanning more than 30 million years of evolution. Gypsy and Mariner elements were involved in the most HT events. While the majority of elements were implicated in fewer than five transfers, we documented a single transposon with as many as with 16 recent transfers, many between different Drosophila groups. In addition, we found that while LTR elements engage in HT more frequently, DNA elements travel longer phylogenetic distances when engaging in HT. This potentially represents a different evolutionary strategy for exploiting naive genomes. Our phylogenetic framework advances the understanding of horizontal transfer dynamics at the species level within Drosophila.