How important are transposons for plant evolution?

For decades, transposable elements have been known to produce a wide variety of changes in plant gene expression and function. This has led to the idea that transposable element activity has played a key part in adaptive plant evolution. This Review describes the kinds of changes that transposable elements can cause, discusses evidence that those changes have contributed to plant evolution and suggests future strategies for determining the extent to which these changes have in fact contributed to plant adaptation and evolution. Recent advances in genomics and phenomics for a range of plant species, particularly crops, have begun to allow the systematic assessment of these questions.