FOREIGN GENE CONTRIBUTION. “In insects for example, it was estimated that ∼2% of the nuclear genome on average (and up to 24%) derives from horizontally-transferred TEs, a figure that likely remains a gross underestimate. The picture is similar in bats where at least 6% of the Myotis lucifugus genome derives from horizontally-acquired Helitrons.” (TE = transposable elements, jumping genes).
https://www.sciencedirect.com/science/article/pii/S0959437X17301685