The evolutionary genetics of transposable element invasions

Transposable elements play major roles in the genome evolution of eukaryotes, and cause harmful mutations, deleterious side effects, and disease. These costs drive their eukaryotic hosts to evolve counter-adaptations, which are so effective that TEs are thought to only survive long term by invading new naïve species. These transposable element invasions appear to occur via horizontal transfer, and can result in the rapid, selfish spread of the element through a species. Despite the evolutionary importance of the host-transposable element relationship, there are still major gaps in our knowledge of how they evolve and persist. Host resistance can evolve astonishingly rapidly, but the evolutionary mechanism by which this happens is unknown. Some horizontal transfer events result in successful invasions, but we have little idea of what factors favour success, or, except in rare cases, how the transfer events occur. This proposal outlines a four-part research programme to address these gaps, examining both sides of the coevolutionary equation. Specifically, I will examine the rapid evolution of suppression from the host side, to understand the population genetics of this process. I will study invasions from the perspective of the transposable element, and ask what genetic factors contribute to their success. To accomplish these objectives, I will take advantage of a unique opportunity-- an ongoing invasion of a model transposable element in a close relative of the genetic model fly. Finally, I will examine the role of parasites as vectors of TEs ,to understand mechanisms of horizontal transfer between species.